Hi Robert.A BSA Red dot sight would probably be the easiest and cheapest sight for the Gamo Big cat.I had one for several years and had it on various rifles.It held up to the recoil of a .22 cal. Benjamin Trail NPXL 1100.This one will fit up to both weaver 5/8 grooves and 3/8 dovetail grooves.They are on sale right now at 47% off for $26:63. Best Wishes - Tomhttps://www.google.com/url?sa=t&source=web&rct=j&opi=89978449&url=https://www.amazon.com/BSA-30mm-Red-Dot-Scope/dp/B000N8MZOI&ved=2ahUKEwiu8oaD-NeLAxUav4kEHe-VBLwQFnoECBwQAQ&usg=AOvVaw2NgHLgcp98liVNGLs6kioI