I carry a 4 inch 629 IWB daily in a holster from Lobo Holsters, I like it a lot
http://lobogunleather.com
I also have a Simply Rugged Pancake for a Ruger GP100 (not quite as big, but close to the 629) that I also like a lot. It has the IWB straps on it.
Nice thing about the Simply Rugged pancake is, you could use it for both IWB and OWB.