I'm a J-Hound, I like they can all share stocks and holsters, of which I have boxes full of ones that don't work for me. These are some of my favorites for the 640-1, and yes I have a Pro, just forgot to get it out for the shoot.
The most versatile for me is the Lobo SL-1, it's comfortable from 3:00 back, and it's easy on and off.
The Lobo Enhanced only really works for me in one spot on my small frame, kinda a pain to get it on with a heavy belt, but I forget it's there, unless I'm driving.
The Simply Rugged is just a solid traditional pancake, rides tight and will work IWB with the loops attached.
Simply rugged Silver Dollar, Lobo Enhanced Pancake, Lobo SL-1. I strung them on a belt so you could see the cants.
LOBO Enhanced and SL-1
Back side
Simply Rugged & Lobo Offset clip IWB
I also like the Lobo Original Pancake, this is for my 66, but you get the idea.
Since they were out, here's some 640's and a NY reload. The silverback is my new Centerfire Internet Special.