I'm not really sure why you'd want to do it. The SP101 isn't really a target pistol. For what it is designed for, fixed sights are fine. You could email all the gunsmiths you can find on the web, but the cost of having it done will probably scare you off.
My wife qualified with a 3" SP101, and hit drop targets at 40 yards with it. Now this ain't exactly bulls eye shootin', but it was the kind of stuff the little Ruger was meant to do.
You'd be better served with buying a 6" 686 if you want to do some real tight paper punching.
