Check out the offerings of Millet.
I have had a SP-1 that was already mounted on a Ruger MKII pistol when I bought it 14 years ago.....it's still on the gun and still working.
I bought a new one about 8 years ago for a model 64 S&W revolver. I mounted it and made a slight change in windage, 4 clicks right, and it was perfectly sighted in. No problems, 10 settings, great value for the money...$60.00 is going amazon price. Easy to adjust , it comes with rings and has easy battery replacement, it is a tube sight , but rugged and reliable with a limited lifetime warranty. I like mine and would buy another.
Gary