Call Ruger. If you don't know the factory part # go to brownells and in the factory parts section get the #'s for the sp,gp,RH,SRH, and BH's. The rear sights are the same on most all Ruger revolvers. Different blades, yes. You can get the factory sights cheap compared to Bowen. Hard to beat Bowen rear sights.
I'd get the complete sight. Eric
Oops!! I think I gave you the wrong info for the SP. I just looked. You want factory part # WO5209 the wo will be white outline.
The nice people at Ruger will tell you what they got.
Eric