Preview:
input[type="radio"] {
    margin-right: 1em;
    appearance: none;
    width: 12px;
    height: 12px;
    background-image: url("checkbox_off.gif");       
}

input[type="radio"]:checked {
    background-image: url("checkbox_on.gif");           
}
downloadDownload PNG downloadDownload JPEG downloadDownload SVG

Tip: You can change the style, width & colours of the snippet with the inspect tool before clicking Download!

Click to optimize width for Twitter