I know you'll need dovetail fitting, but I have a set of these on my Impact, and they are very good
https://www.opticswarehouse.co.uk/ve...icatinny-rings
or medium height
https://www.opticswarehouse.co.uk/ve...icatinny-rings
You can get a pair of snap in weaver/picatinny to 9/11mm adaptors off that famous auction site for around £6..... on a tame HW77 they should be fine
TX200 .177 21mm TL | TX200HC .22 22mm TL | Prosport .22 22mm TL
HW40 | HW45 | Diana Mod5 | Webley Senior....... Because PCP is like kissing your sister (apparently)