I'm looking for a HI-VIZ type sight that mounts over the bead on a 870. I don't really want to drill and tap the barrel. What works well? Links?

Thanks.

870's tend to shoot center of bead.  Installing anything over the top will mean that the gun will shoot below bead for one. And the second point which is really the deal killer, anytime you stick something glowing on the front end of the barrel, it pulls your eye to the bead, and fades out what you are trying to hit.

If you want to do it right, have a white bead installed in place of the old brass bead, and maybe even have a center bead installed to give you better idea of if you are pulling your head off barrel line/the stock during the shot.