I have a new in the box model LG-207 Crimson Trace Laser Sight Grip that fits many Smith and Wesson revolvers of K,L, and yes (believe it or not, thanks to a clever spacer) N frame. It will work on round or square butt models. There is a list of models that it fits on the side of box, see pictures below. The cheapest I've seen these were on Amazon for $131.99.
Asking $85 shipped
IMG_0877.jpg
IMG_0881.jpg
IMG_0875.jpg
IMG_0874.jpg