Hi all. I have a Sears 60mm with the diamond Z mark, which I read here was made by Tanzutsu. It looks decent and the optics seem pretty good (daytime test), but the pinion on the 2-sided focus knob is totally stripped (rack is OK). Can anyone give me an idea of where to start looking for a replacement? The whole piece is 3" long, and the inner rod (w/pinion) is 2".