S&W 686 grips

They sure look like Altamont Grips, but I'm not finding them. Good luck!

Those are the grips that come with the M686 Deluxe which is being distributed by Talo. They are Talo exclusive.
http://www.taloinc.com/smith_wesson.htm

Altamont makes them, but I don't know if you can order them.

They are made to fit current round-butt S&W K and L frames, as all square butt frames have been discontinued on regular production revolvers. They convert the round-butt to a square-butt configuration. Altamont, who make a lot of special limited-run stocks for a number of manufacturers might, or might not, offer them for the older square-butt L frames.

Back when... Smith & Wesson was still making square-butt K and L frame revolvers they also made "target stocks" somewhat similar to the ones you are looking at. Shop around Ebay and other Internet auctions and you might find a pair.