it's not going to be easy....
Here's what I've found.....
The PT-111 is to big for pocket carry (and I'm not exactly petite).
The PT-111 Mil. Pro. didn't fit in a holster specifically listed as being for the PT-111 Millennium.
After many e-mails, most all of the high end holster makers I contacted won't make a holster for the PT-111 Mil. Pro. and don't appear to have any intention of getting the forms to do so. My speculation (and nothing more than that) is that they don't think people will spend big $$ for a custom holster for a brand of gun with an economy reputation.
The high volume makers (Galco, etc..) don't have the Mil. Pro. on their gun list, but, I have a hunch (and that's it) that the PT-111 Mil. Pro. may do fine in a holster made for a Glock 26. Make sure you understand the return policy if you roll the dice on this one.
Milt Sparks said they could make me an IWB (I wanted a Watch Six) for the PT-111 Mil. Pro. But the waiting list is 6 to 8 MONTHS!!
Fist also said they could make holsters for the PT-111 Mil. Pro.
After a lot of frustration trying to find a holster, I'm carrying my PT-111 Mil. Pro. IWB @ 4:30 with a clip draw installed on the right side of the poly frame. There's lots of opinions about holsterless carry (just do a search under "Mexican" carry). So you have to make a decision about that first. I don't run, jump or climb when I carry (or ever to tell the truth) and after 6 months I haven't had the piece drop or shift at all. I find that drawing with the clip draw is no trouble at all ..... BUT..... "holstering" (don't know what else to call it) is a little bit of a pain. So if you want to stash the piece in your truck console and slip it IWB when you get out.....it ain't a gracelful maneuver. I drive with the piece IWB with the clip draw (you can pivot the gun slightly if you want) and though I know it's there, I can live with it.
I hope this helps.