Best holsters I've found for carrying a 6" K frame are the old police leather ones with a swivel, but they're OWB. If someone could reverse design one of those for IWB it would probably work wonders.
Check out MTR Leather. I was able to get an IWB from them for a 4" K frame. It's a lot like a Crossbreed. I'm sure they would be able to set you up for your 6". Not the most comfortable carry but it works.
MTR Custom Leather