Very nice! I love the satisfaction of making something useful out of
stuff I already have just laying around the shop.

A piece of Corian or something similar would look great if you think you
have the tools and the know-how to work with it. Personally, I would
stick with theme of the oak frame. Glue up a rectangular slab from 3/4"
or thicker oak boards (unless you already have something wide enough),
cut it on a 45 large enough to give you a little bit of overhang on the
front, and maybe put an ogee or a roundover on the front.

Charlie