No, afraid not.
I've read about a 12 shot magazine for the PT145, but, can't find one. I talked to a gunsmith about attaching a piece of hard rubber to the bottom and shaping it.
I don't know.
I bought a 24/7 at a gun show Saturday just to solve the problem until I come up with something.
Let me know if you find one.
I have the same problem with my PT-111. I got it for the ease of concealment, but hate carrying it now because my little finger doesn't even come close to fitting on the gun. The PT-111 Pro looks like it comes with one, but I can't find one for my older model anywhere...