I'm on my third, and so far most comfortable, IWB tuckable holster, the MTAC by Comp-Tac. But it isn't made for the P-64 or CZ-82 (which is mentioned in your title, but not the body of your post.) The Crossbreed SuperTuck is supposed to be just as comfortable as the MTAC, and it IS made for the CZ-83 but not the P-64. Now the CZ-82 and -83 are slightly different, and some holsters that fit one don't fit the other, but some holsters fit both. If you are looking for a CZ holster I'd call Crossbreed and ask 'em. I don't know WHERE you'd go for an IWB tuckable P-64 holster, though - even FIST, which has one of the longest gun lists out there, doesn't show the P-64 as an available option.
on the P64 forums theres a guy named Pfunk (or something very close. He's als a mod there) he makes IWB quality leather holsters spacificaly for the p64. I dont own one but everyone there seems to praise the quality, fit and finish. I believe they are about $60 or so.