Those combats look great on the 640. That would be my choice for a steel J-frame.

For lightweight carry I am liking the alloy grips from EFF. They are small, light, weatherproof, and slide out of a pocket or holster easily. Unlike wooden checkering, the checkering on the EFF grip will never lose its bite. Also, the similar materials of the grip and frame seem to transfer recoil more evenly than comparably-sized (minimal) wood grips. And...they look cool.