I take it you are talking about a shotgun, there are a lot of after market sights out there.
I have one of these on an old shotgun and it works good, or at least I can hit the target with it.
Have you tried using optics many companys make after market scope mounts for shotguns.
Ya iv seen those for vent rib barrel but im looking for sights meant for a plain barrel.Haven't looked for a long time but I remember Walmart used to have a set (green front, amber dual strip rear) of fiber-optic sights that just slid into a vent-rib barrel and clamped down by tightening a set screw on the side. Might peruse their sporting goods section if you haven't.
Ya iv seen those for vent rib barrel but im looking for sights meant for a plain barrel.