Potentate,
Honestly I don't think you'll have very good luck finding an aluminum radio box, being that it's one peice making that all aluminum would not only be much heavier but also pretty expensive.
If you're looking for a custom look, one thing I've thought about doing is maybe adding some chrome vinyl to the box. You can get the vinyl in different colors and I know there's one or two members that could probably hook you up for a small price if not then your local auto zone or simliar auto shop could.
-Michael