Allow scrolling and clicking to go through an overlapping Div

Allow scrolling and clicking to go through an overlapping Div

A client's website design is dark teal and he didn't like the scroll bar
since it ruins the rest of the style. He also wishes I do it without third
party libraries and a way he can hopefully understand. So the only way I
can think of doing that was creating a div, setting it to position:
absolute;, same background-color as the rest of the theme and then setting
opacity: 0.8; so that it looks 'blended' in better.
He is happy with the result, since it works for all browsers, he thought I
even created my own scroll-bar when he first saw it. The problem however
is, if a person would like to actually click on the scroll bar, they can't
because there's a div above it. Is there any way I can allow a div to be
visible, but all the clicks and hovers and everything go through it to the
next div? Scrolling also does not work when above the scroll bar because
i'm in the div that's overlapping the real div that actually has the
scroll bar.
Any help is greatly appreciated.