My choice is the Greg Kramer IWB #2 holster in horsehide or his Belt Scabbard. The scabbard is very low profile for an on the belt holster.
Both are extremely thin for leather because horsehide is denser than cowhide holsters are. It is more durable, too.
For the pocket, same maker, Kramer. His pocket holster has a plastic or polymer rectangle sewn on the outside so if it prints in your pants pocket it will look like a wallet. It will not print the profile of the PPK, or a J Frame S&W or a D frame Colt. Release from the holster in the pocket is faster than with the nylon or nylon-like materials used for the DeSantis Nemisis or the Mika pocket holsters. This material is also thicker than horsehide leather and adds a little more bulk to the holster as well.
The Nemisis and the Mika both work, and they are very affordable. I used a Nemisis for a little over 2 years for front pocket carry.
However, you get what you pay for.
I'd suggest checking out Greg Kramer, Milt Sparks, Ken Null, Mitch Rosen, or Matt DeFatti before you buy anything. All these makers are fairly expensive but they are some of the best in the US.
Kydex holsters are even thinner than horsehide. They are inexpensive, too. The bad points are that Kydex is like sandpaper to a blued gun's finish. If your PPK is a old German one or an imported post war version I think you will be miserable if you carry it in a Kydex holster when you see what it does to the finish. If you have a newer US made stainless steel PPK, then you have nothing to worry about.
* I just noticed you mentioned your PPK is stainless steel. One less thing to worry about if you want a Kydex holster.
It is also my experience that Kydex holsters, being quite rigid, become uncomfortable after a few hrs. of wearing. If you intend to wear the holster and gun for 4+ hrs. leather will be a lot more comfortable.
Just my two cents worth.
Good luck!
