Buying Wolf Gold or Prvi Partizan (same ammo, different label?) and then reloading the ensuing empty cases seems like the best method of late.
Supposedly... I have heard at gun shows, gun shops, and the range that there are simply masses and masses of GP11 stockpiled in Switzerland that are "on their way." Whether they are waiting to clear customs... or for the Swiss to OK the whole thing... or for some other unknown factor, I don't know. But I don't think we've seen the end of that fantastic GP11.
If you're lucky, you can still find a Big Black Brick of it at gunshows, if you go VERY early on the first day and ask specifically for it. Prices are about $170 or so now, depending on the dealer. I've seen as high as $225, and it was long gone by the time I got there.