Re: 5.25" Psu To Power System + Gtx260?
Unfortunately there is no such thing. You could try to relocate your current PSU into the bay area on it's side, but you'd probably be just as far ahead to get a different case.
The build quality on the few 5 1/4" PSUs that are on the market isn't all that great, and they simply cannot power very much. Some of them might not even handle a GTX 260.