There is a Ghost Ring kit available from Mossberg but its not real cheap. It looks cool but i'm not sure if it would be compatible with a top-fold stock or not. Tru-Glo has a nice set of high viz sights as well. I just have my front bead and it works good enough for me. If you are planning to use a lot of slugs I would go with a rifled barrel and being as they usually come with sights anyways your problem would be solved.
Well mine has the factory heat shield. I tried one of those heatshields with the built in sights, and it was junk.
I am looking for something that will bolt down to the factory holes in the receiver.
The front bead unscrews, so there should be something that will attach there.
I suppose if I could find a rail that would attach to the factory holes in the receiver, I could go with one of the mini red dots...these eyes arent getting any better.
I've bought the Mossberg ghost ring kit before, and installation kind of sucks because you have to weld / braise / or solder on the front sight. I also added a Meprolight sight in mine.
On my other Mossberg, I simply added a Tritium bead, and like it just as well.
Another option would be to add a weaver mount and red dot.
I wouldn't suggest the heat shield combo things. Most are pretty junky and made of polymer.