With mice, the screws are always hidden by the glide pads on the bottom. It looks like an ASUS WT200 but after a quick look I can’t find any for sale.

Ok if you can’t get replacement guts, it might be something easy you can fix. Maybe some paint got on the laser or the lens. Flip it over and have a close look at the little hole. Some isopropyl and a q-tip might get it working again.