The Vector Optics Maverick-III Magnifier is a highly robust combo for your red dot sight.  It mounts easily onto standard picatinny rails and works with an extremely wide array of standard red dot sights! This particular magnifier has a push-button style locking mechanism that allows it to stay in places when folded.

Vector Optics Maverick-III 3x22 Magnifier MIL
Rubber Armed
Fully Multi Coated
A Monocular 3 Times Magnifier
Adjustable Windage & Elevation
Crystal Clear, 2.7" Long Eye Relief
With SCTM-17 Flip Side Picatinny Mount
36mm 1.4" From Bottom to Ring Center
49 Feet @ 100 Yards Field of View
Compact, Solid and Light Weight for All Application Tactics, Hunting & Sporting