Boxhead
Member
Looking for suggestions for replacement non-finger groove combat grips for my 657-4 I recently picked up. Appreciated in advance.

What you're looking for is a style called "banana". Check out the "Retro Banana" grips on the Ahrend grip website:
Ahrends Grips : Smith & Wesson Retro Grips
Or you could modify what you have, you would not need to be concerned about having to refinish them after wards.
Since they are the resin impregnated laminated "dymondwood". All that needs to be done is sand them smooth with 400 grit sandpaper and buff them out with a cotton cloth.