how can I add scrollbar and edit its style

[doraemoncandy]

i really love this style of selection box! however, i have a lot of option in selection...
so i need to add scrollbar in it. but when i add scrollbar, its style is not suitable with the original
like this picture (it's very strange in visual)

Therefore, i want to change the scollbar style like below

i have used the " css ::-webkit-scrollbar" , it works in chrome but not in firefox
i want to use a way to across browser so i find jquery way to do that.
but seem to lots of jquery way having some problmes...
( i also tried to use the jscrollpane ((http://jscrollpane.kelvinluck.com/)) , lots of pepole recommand that. but it can't work)
can any way to solve that?
thank you and forgive my poor english..