Google on "allchin" mounts.
I put a red dot on a 66 using a (Raptor) mount sold by a fellow who used to make and sell them in the classifieds here 7-8 years ago. Awesome machining...
FS: Reflex Sight Mounts for Smith & Wesson Revolvers and Pistols
Seems like he disappeared about 2020.
His mounts were made to work on any S&W K/L/N frames with the extra tapped hole in the topstrap beneath the adjustable sights. Any other would require DIY drilling and tapping.
I put one on a J frame 317, the first such equipped J I've ever seen.
It required drilling and tapping a hole and a little file work to make the rear settle down over the frame. The whole package weighs< 14 oz and the little gun will empty all 8 shots into 1.5" at 50 feet. I don't believe a finer kit gun exists.