Great question, and I've been on the same search. So far, the answer seems to be "Horsehide Del Fatti with offset clip ...but his lead time is over 18 months now..."
I understand the part about the offset clip: keep it over the trigger, not over the fattest part of a revolver, the cylinder, which most readily-available J-frame IWBs seem to do. Makes sense to me.
I have and like Crossbreed Supertucks and QuikClips for larger guns. Seems to me someone must make a quality J-Frame IWB with one metal clip, offset, that doesn't take a year-and-a-half to get.
To further muddy this up, I need one that will accommodate a 2-1/2" bbl, so an open muzzle-end is a "must-have" since no one seems to be making holsters specifically for the relatively-new 2-1/2"bbl S&W J-Frames yet.