Try Lobo Gunleather. Ray is on the S&W forum, and does great work. I'm getting the IWB offset model for my 640, but your gun would probably need a sturdier holster.
Today was the first day i set-out looking for one the gun/gun accessories stores i went to that had a holster that fit were all uncle mike's holsters, one of the sailors (sales people) did mention lobo. I wanted to buy local but it looks i'm going to have to get over that
Zeeman hit the nail on the head by mentioning Lobo Leather. They make a really good holster. Closer to home, R Grizzle makes some really good holsters as well. Ordering will take some time with these two. Galco makes a decent holster. You may want to search e-bay and see what is available.