termiflyer,

I would recommend a cheap red-dot, either a Bushnell or BSA can be had for $35-55.

I would then suggest a B-Square mount, and Burris Signature Zee rings.

Of course the mount ($45) and the rings ($30) will cost more than the scope, but you won't need to worry about rattles or "loosening" on your shotgun. The B-square also comes with rings, so you could save some dough by skipping the higher quality Burris rings. Can get them all at Natchez shooting supply...