It is a tough search for exactly the right holster. Which model are you looking at?
Kydex "Trapp" Holster
I'm in the process of looking too for my M&P .40 FS. I'm looking for one for OWB and one for IWB. I think I want leather for OWB.
IWB not sure.
Be careful with some of the Hybrids. Reason is they flatten out when the gun is drawn. Here is a picture of a AlienGear (exactly like Old Faithful and Crossbreed and others). The ones like Crossbreed might have a better chance as the shell is attached directly to the leather rather than on adjustable stand-offs. This is another member on this forum.
I'm trying to find/make a unit with a full wrap-around-the-gun style (like the Kydex, Blade-Tech, Crossbreed and others) that can be used IWB without crushing from belt pressure. Most of the ones available are just the outer shell and won't hold the pressure.
The search continues...links to most mfgs.
Holsters