I personally carry a Walther P99 compact with the A/S trigger. But there are some FNP owners that can speak up. I also think there are a few past holster threads that might help U. And, Crossbreed Holsters sells holsters for the FNP.
My FNP9-M. Best pistol I've got really. It's not the best looking, not the most accurate, nor the most powerful, but it points the best and is the most reliable. Having already abused it in little backyard test, it's got my vote. Holster I used to have for it was a passport kangaroo holster. Just a general IWB/OWB large frame compact auto holster.
Haven't bought the FNP 40 yet, but when I was looking at one in a gun store I tried it in a Galco Matrix MX7 holster for the Sig P229. That's the holster that I use for my M&P 9mm. The FNP seemed to fit in it better than the M&P. I haven't tried carrying an FNP in that holster, but I seem to recall seeing somewhere that holsters for the P229 will fit the FNP.
I've HEARD that the USPcompact holster works great. Also the XD holsters.
I've personally put my FNP9 inside a Don Hume IWB fullsize USP holster and it seemed like it would work, but I thought it would be better if it was a little tighter. So..... the USPcompact holster idea makes sense.
If don't want to spend mucho $ and IWB is ok, an Uncle Mike's # 15 fits perfect.Take s strip of 1' Scott's rubber tape, add strip of velcro to back of tape and stick it to front inside of holster and it will stay open enough for fairly easy reholstering.