Nills (Nill Griffe) makes some fabulous grips for round butt K and L-frame guns like your 686 that duplicate the famous "coke" grips that Smith put on their revolvers. They are the same shape and appearance as the original "cokes", following the curve of the grip frame and ergonomically perfect. They're made out of walnut and Nills sells them in natural wood and unlacquered. As a result, the grips darken with time and use. They give the round butt revolver the appearance of a square butt gun. I have a set on my 686-6 and they are absolutely fantastic, the prettiest and most comfortable grips that I own. They're more comfortable than rubber grips, at least for me, and I can fire even full house magnums from the gun without experiencing the slightest discomfort.
They're not cheap. Nills is charging about $250 for a set. I think they're worth it, personally, but, still, that's a lot of $$ for grips. Btw, original "coke" grips in good condition now sell for more than that which Nills charges for its reproductions.
Over on the Smith & Wesson forum you'll find a fellow named Kurac who makes his own "coke" reproductions. He charges about $125 or slightly more for a set and they are great. I've put a set of his grips on my N-frame Model 27 and on my K-frame 617 and I love 'em. He makes his grips out of a variety of woods and you may custom order from him.