These are the only places that I know of... Ebay LikSang GBAX PlayAsia
I ordered mine from Gbax, it was 150dollars for the gamepark, 30 dollars for shipping. It also came with a cd that had gp32 related software/games on it.
If you're going to spring for the FLU, GBAx has the best price. For a non-FLU, Lik-Sang, GBAx and Play-Asia are all about equal. GBAx is probably the only place with half-competent tech support, though.
Just as a little aside for those not in the US (I'm in Canada), GBAx is *far* cheaper for FLU units than anyone else. They're a little cheaper (after exchange), but they'll also mark it as a gift package with a value of 50 pounds, so you won't get dinged with like $50 extra in duty.