以下のコードをカスタマイズ > デザインCSSに入れてください。

.social-buttons ul {
  padding: 0;
  margin: 0;
}
.social-buttons ul li {
  display: inline-block;
  margin: 0;
  padding: 0;
  list-style-type: none;
  width: 15%;
  border-radius: 3px;
  vertical-align: text-top;
}
.social-buttons ul li a {
  width: 100%;
  display: inline-block;
  color: #fff;
  text-decoration: none;
  position: relative;
  text-align: center;
}
.social-buttons ul li a span.share-count {
  display: inline-block;
  width: 100%;
  color: #000;
  background: #fff;
  line-height: 2rem;
  border-radius: 3px 3px 0 0;
  opacity: 1;
  -webkit-transition: opacity 0.4s, transform 0.4s;
  transition: opacity 0.4s, transform 0.4s;
}
.social-buttons ul li a i {
  padding: 0 5px;
}
.social-buttons ul li a i.blogicon-plus {
  color: #dd5144;
}
.social-buttons ul li a svg {
  position: absolute;
  left: 0;
  right: 0;
  margin: 0 auto;
}
.social-buttons ul li a svg path {
  fill: #fff;
}
.social-buttons ul li a span.share-label {
  font-size: .7rem;
}
.social-buttons ul li a:hover span.share-count {
  opacity: 0.8;
}
.social-buttons ul li.hatena {
  background: #00a4de;
  border: solid 1px #00a4de;
}
.social-buttons ul li.facebook {
  background: #3e59a5;
  border: solid 1px #3e59a5;
}
.social-buttons ul li.twitter {
  background: #1b95e0;
  border: solid 1px #1b95e0;
}
.social-buttons ul li.googleplus {
  background: #dd5144;
  border: solid 1px #dd5144;
}
@media (max-width: 767px) {
  .social-buttons ul li a span.share-label {
    display: none;
  }
}

これで完了です。

このサイトの場合はいろいろ DOM 操作をやっていますのでもともとやや重めですが、このソーシャルボタンに変更したら、８秒くらいかかっていた読み込みが４秒くらいになりました。

以下は、Javascript の圧縮前のソースです。

Javascript 可読版

/*--------------------------------------------------------------------------*
 *
 *  はてなブログ用ソーシャルボタン
 *
 *  Copyright (c) 2016 IMUZA.com http://www.imuza.com
 *  Released under the MIT license
 *  http://opensource.org/licenses/mit-license.php
 *  
 *--------------------------------------------------------------------------*/


(function(){
  var getGoogleShareCount = function(obj, callback) {
    var url = 'https://clients6.google.com/rpc?key=AIzaSyCKSbrvQasunBoV16zDH9R33D88CeLr9gQ';
    var xhr = new XMLHttpRequest();
    xhr.onreadystatechange = function () {
      if (xhr.readyState === 4 && xhr.status === 200) {
        var obj = JSON.parse(xhr.responseText);
        callback(obj.result.metadata.globalCounts.count);
      } else {
        callback(0);
      }
    };
    xhr.open('post', url, true);
    xhr.setRequestHeader( 'Content-Type', 'application/json' );
    xhr.send(JSON.stringify(obj));
  };


  var getCountByJSONP = function(url, count, callback) {
    var script = document.createElement('script');
    script.type = 'text/javascript';
    var callbackName = 'ExternalCallback_' + count;
    window[callbackName] = function (data){
      if(script.parentNode){
        script.parentNode.removeChild(script);
      }
      try{
        delete window[callbackName];
      }catch(e){
        window[callbackName] = null;
      }
      callback(data);
    };
    script.src = url + '&callback=' + callbackName;
    document.body.appendChild(script);
  };


  var getFbShareCount = function(url, callback) {
    var xhr = new XMLHttpRequest();
    xhr.open('get', url, true);
    xhr.onreadystatechange = function () {
      if (xhr.readyState === 4 && xhr.status === 200) {
        var obj1 = JSON.parse(xhr.responseText),
          obj2 = 'share' in obj1 ? obj1.share : {},
            count = 'share_count' in obj2 ? obj2.share_count : 0;
        callback(count);
      } else {
        callback(0);
      }
    };
    xhr.send(null);
  };


  var count = 0;
  var tmpl = document.getElementById('tmplShareButtons');
  tmpl.removeAttribute('id');
//（2016/9/6）修正
// about ページで、記事ではない article を取得をしないようにクラス名に変更
//  var articles = document.getElementsByTagName('article');
  var articles = document.getElementsByClassName('hentry');
  Array.prototype.forEach.call(articles, function(article) {
    var bm = article.getElementsByClassName('bookmark')[0];
    var permalink = bm.getAttribute('href');
    var title = bm.innerHTML;
    var clone = tmpl.cloneNode(true);


    var hatenaButton = clone.getElementsByClassName('hatena-bookmark-button')[0];
    hatenaButton.setAttribute('href', 'http://b.hatena.ne.jp/entry/' + permalink);
    hatenaButton.setAttribute('data-hatena-bookmark-title', title);    
    var url = 'http://api.b.st-hatena.com/entry.count?url=' + encodeURIComponent(permalink);
    getCountByJSONP(url, count, function(data) {
      hatenaButton.getElementsByClassName('hatena-bookmark-count')[0].innerHTML = data;
    });
    count++;


    var facebookButton = clone.getElementsByClassName('facebook-share-button')[0];
    facebookButton.addEventListener('click', function() {
      FB.ui({
        method: 'share',
        href: permalink,
      }, function(response){});
    });
    var url = 'https://graph.facebook.com/?id=' + encodeURIComponent(permalink);
    getFbShareCount(url ,function(data) {
      facebookButton.getElementsByClassName('facebook-count')[0].innerHTML = data;
    });


    var twitterButton = clone.getElementsByClassName('twitter-button')[0];
    twitterButton.setAttribute('href', 'http://twitter.com/intent/tweet?url=' + encodeURIComponent(permalink) + '&text=' + title);
    var url = 'http://jsoon.digitiminimi.com/twitter/count.json?url=' + encodeURIComponent(permalink);
    getCountByJSONP(url, count, function(data) {
      twitterButton.getElementsByClassName('twitter-count')[0].innerHTML = data.count;
    });
    count++;


    var googleButton = clone.getElementsByClassName('googleplus-button')[0];
    var w = 500, h = 500, x = (window.screen.width - w ) / 2, y = (window.screen.height - h) / 2;
    googleButton.setAttribute('href', "javascript:void(window.open('https://plus.google.com/share?url=" + encodeURIComponent(permalink) + "', '_blank', 'width=" + w + ",height=" + h + ",left=" + x + ",top=" + y + "'))");
    var obj = {
      "method":"pos.plusones.get",
      "id":"p",
      "params":{
        "nolog":true,
        "id":permalink,
        "source":"widget",
        "userId":"@viewer",
        "groupId":"@self"
      },
      "jsonrpc":"2.0",
      "key":"p",
      "apiVersion":"v1"
    };
    getGoogleShareCount(obj, function(data) {
      googleButton.getElementsByClassName('googleplus-count')[0].innerHTML = data;
    });


    article.getElementsByClassName('social-buttons')[0].appendChild(clone);


  });
  tmpl.parentNode.removeChild(tmpl);
})();