Sure! In your CSS, add the following:

At the top:

html {
    overflow-y: auto;
    background-color: transparent;
}

Then, right AFTER the “body” property (also near the top), add the following…

@media screen and (min-device-width: 1025px) {
    body {
        position: absolute;
        top: 0;
        left: 0;
        bottom: 0;
        right: 5px;
        overflow-y: scroll;
        overflow-x: hidden;
        }

    ::-webkit-scrollbar {
        width: 14px;
        height: 6px;
    }

    ::-webkit-scrollbar-button:start:decrement,
    ::-webkit-scrollbar-button:end:increment {
        height: 5px;
        display: block;
        background-color: transparent;
    }

    ::-webkit-scrollbar-track-piece {
        background-color: transparent;
        -webkit-border-radius: 7px;
    }

    ::-webkit-scrollbar-thumb:vertical {
        height: 0px;
        background-color: #ccc;
        border:1px solid #b5b5b5;
        -webkit-border-radius: 7px;
    }

    ::-webkit-scrollbar-thumb:horizontal {
        width: 0px;
        background-color: #bbb;
        -webkit-border-radius: 3px;
    }
}

NOTE: This will only work for WebKit browsers (Safari, Chrome). All the other browsers can suck it. ;)

Also, if you’re in the Tumblr dashboard and want to see what this is about, go here.