Tru Glo Clamp on with windage and elevation adjustment capabilities.
However you can get by with just a normal bead sight on a shotgun. Lots of birds taken with that method.
The real problem is you will cheat. And ever so slightly lift your head before the shot. Thus a miss or worse yet a cripple.
What sights really do is help the shooter keep their head down and concentrate on sight alignment on their target.