Look at the manual for the gun here: http://www.smith-wesson.com/wcsstore/Walther/upload/other/P22_usa_Manual.pdf
You'll find the parts list and exploded drawing near the back. Find the parts you need, call S&W and order them. I can't tell from the diagram, but it looks like a simple dovetail mount.
You'll find the parts list and exploded drawing near the back. Find the parts you need, call S&W and order them. I can't tell from the diagram, but it looks like a simple dovetail mount.