My 10/22 had an aluminum see-through picatinny riser attached wth 4 screws into the receiver when I bought it. When I installed brand new Tech-Sights (TSR-200...awesome!!!), I couldn't get the 4 screws removed so I destroyed them with my screw extractor. Now that I want to install this riser on another 10/22, I need 4 more screws. Anybody know the type of screw I could/should use?