Front Ring-sight for a Mossberg 500… do they exist?

After searching high and low, I’m stumped.

I’ve got a Mossberg 500 in riot-gun config (18 inch barrel), and I’ve been hunting for either a front ring sight or a front ring-and-post sight to replace the tiny OEM brass bead sight.

Ghost rings are out, because it’s got a Choate top folder stock, and it isn’t tapped for rear sights to boot.

Yeah, I know, a sight probably isn’t even necessary with this configuration, but I’d like to have something more than the bead up front. It’d be nice to be able to look through a “circle of death”, for lack of a better term. 😆 😯

Anyone know of any screw-in replacements that fit the bill?

Thanks…