JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" class="combobox" />

CSS

.cb-arrow {
    cursor: pointer;
    background: -moz-linear-gradient(center top, 
        rgb(242, 242, 242) 0%, 
        rgb(221, 221, 221) 50%, 
        rgb(207, 207, 207) 100%) 
        repeat scroll 0% 0% transparent;
    border: 1px solid #707070;
    -moz-border-radius-topright: 3px;
    -moz-border-radius-bottomright: 3px;
    padding: 0 3px;
}

JavaScript

$('.combobox').after('<span class="cb-arrow">&#9660;</span>');