The only sight improvement that I ever did was to D&T a
S&W M-10-8 4" barrel, add a Weaver Base, and add a Tasco Red Dot.
I built this for bowling pin shooting, but, it turns out, that I prefer to use a carry gun with the iron sights.
That said, I think that Weigand Combat offers a fixed sight to replace the adjustable kind. I believe it just screws on, in existing holes. I recall reading an article about it on their site. Do a search on Weigand Combat.

Bob