JSFiddle - React, Tailwind, and code Playground

HTML

<body><div class="outer">
   <div class="icon" id="ico"></div>
   <div class="content">
       bla<br/>bla<br/>bla<br/>bla<br/>bla<br/>bla<br/>bla<br/>bla<br/>bla<br/>
   </div>
</div>
</body>

CSS

.outer {
    position: relative;
    height: 100px;
    overflow-x: hidden;
    overflow-y: auto;
    width: 100%;
}
.icon {
    position: fixed;
    top: 0;
    background: red;
    width: 10px; height: 10px;   
}

.content {
    width: 100px;
}

JavaScript

function getScrollBarWidth () {
  var inner = document.createElement('p');
  inner.style.width = "100%";
  inner.style.height = "200px";

  var outer = document.createElement('div');
  outer.style.position = "absolute";
  outer.style.top = "0px";
  outer.style.left = "0px";
  outer.style.visibility = "hidden";
  outer.style.width = "200px";
  outer.style.height = "150px";
  outer.style.overflow = "hidden";
  outer.appendChild (inner);

  document.body.appendChild (outer);
  var w1 = inner.offsetWidth;
  outer.style.overflow = 'scroll';
  var w2 = inner.offsetWidth;
  if (w1 == w2) w2 = outer.clientWidth;

  document.body.removeChild (outer);
  return (w1 - w2);
};

var scrollWidth = getScrollBarWidth ();
var ico = document.getElementById('ico');
ico.style.right = scrollWidth + "px";