I've been looking for recommendations for OWB holsters and maybe some IWB's also.
From what I've been able to gather, the PF940C frame is very similar to a factory Glock 19 with the exception of the trigger guard and the frame portion under the slide just above the accessory rail is wider so
it won't fit many holsters molded for the Glock 19. I'm not really into leather or nylon holsters, mainly dealing with molded plastic or kydex here.

Anybody know if the Pf940C frame will fit in a Blackhawk Serpa for a Glock 19?

This article touches on the holster issue and recommends the Safariland GLS line. Recoil Web Article

I'm wondering if the Blackhawk Ominvore might work, too but I don't really care for the retention mechanism. Omnivore

Lenny is pretty optimistic that it will fit factory Glock 19 holsters but notice that 4 of the 5 holsters he shows are flexible and have some give to them.

If you go to the glockstore site, or view the video on the pf940c they state that the Glock 30 holster fits. That said, I prefer leather for IWB and have the GLS for OWB. It does fit the GLS well.

Ordered a Glockstore "$35 Holster" for a Glock 19 and it isn't too bad. 
At first I was not impressed with the amount of retention but I realized I wasn't pushing it in far enough so I gave it a firm push into the holster and it locks in like it should.
Carried OWB last night and I'm happy with it.

Attempted to disarm myself the other night and the pistol would not come out of the holster!
Totally locked in with no chance of pulling it out. Figured out that the pistol had actually entered too far into the holster
and the last rail section caught on the end of the holster. I'd been dead meat if I would have had to draw it in a hurry.
I had not touched the tension screw since I bought it so I checked it and I figured out that it was a bit loose. I tightened the screw all the way
down until it was tight and did several dozen test draws-everything seems to be fine.

Did you order one sized for the 19 or for the 20/21 like they suggest?

This is what I messaged their customer service on March 29th:

"I watched Lenny's video on youtube published on March 15 and he said the Polymer80 PF940C will fit in your $35
Dollar Kydex Holster. Do I buy the 19/23/32 model holster or do I need
to get a bigger size?"

This was their reply:

"Yes, that is correct, the compact polymer80 will fit in the $35 holster built for the 19/23/32 models."

So I ordered the one for the 19/23/32. I have not had any issues except that one but I resolved it by tightening the tension screw.

I think I would take a heat gun to the end of the holster where it caught on the rail and flare it out slightly so it couldn't happen again but that's just me.

Great idea. Thanks

My thoughts exactly. Also while you have it out I'd do a little reforming around the trigger guard due to the differences in the frames.

I bought the stuff to make my own. Hopefully I find some time this weekend to get it done.

If you like leather... and are using a stock G19 slide profile... Mine fits very nicely into M&P 4.25" leather.

I've got a Frontline 'summer special 2' type holster for the M&P that my Poly80 compact fits like a glove into.
It fits into other M&P leather as well.

I've read in various places that Glock 20/21 holster work as well, but haven't tried my 20sf holsters as the M&P leather fits so nicely.

Pro tip  if you are using a leather holster for a different gun in approximately the same size and reform the holster 

Roll your own

Or you could sell me that one, since it's exactly what I'm looking for. And you can obviously make another.

Actually...that may be an option once I get an Inforce APLc for it. I'll have to press a new set for this gun anyway. I also have a matching OWB for this setup that I'd have no more use for. IM me if your interested.