Unless you are going to spend the big money for an original mount and have the receiver drilled and tapped etc. Your best option is a handgun scope. Without any permanent alterations you can remove the rear sight and mount a scope on it.
Yeah I'm not sure. My scope budget is about $100. I do have a bsa red dot. It's not bad for what I paid. I just put a centerpoint on a guys m&p. It seemed decent.
I'm honestly more of an iron sights guy.