wow $500 is a LOT of money for a rocker cover billet or otherwise.
surely it wouldn't cost that much to have one (or multiple) cnc'd up?
edit: just had another idea, what about a stainless steel...??!!
my fabricator could do these im sure.
here is something that he does, apart from the fittings it looks seamless.http://img32.imageshack.us/img32/1031/f1110209m2232060.jpg