I carry a Kahr PM40 in a pocket when riding a motorcycle, it fits in either an outer jacket pocket or the inner pocket of a leather vest.
The Kahr PM40 is a pretty nice package - it is essentially identical in outer envelope size to a S&W J-frame like the 640, etc. - but thinner than the cylinder.
If I were in the market for a true pocket pistol, I think I'd be inclined to go with the .40 S&W versus the .45, just because the external dimensions tend to be just a bit smaller all around.
I'm real happy with the Kahr PM40, and if you're looking for something like that would encourage you to see if you can't borrow one from a friend and see how it fits your hands.
Treat everyone you meet with dignity and respect....but have a plan to kill them just in case.