Most of the lights on the back of my bus show signs of allowing water in (rust on the inside) and on the outside the heads of their retaining screws are all rusted as well. Here is a pic of one of my lights with the screws out: https://imgur.com/a/bRwJhVe
I'm thinking that to begin with, I want to replace that circular gasket. Are gaskets like this available from any online stores as OEM materials? If not I was thinking it would be easy to cut new ones, but I'm not sure of what material to use. I scoured Home Despot and couldn't find anything like a rubber mat or whatever this material is. Would an auto parts store have something like this?
Or would it make more sense to not worry about replacing the gasket, and instead use auto seam sealer around the base of the light? I could see that being more effective for sure, but I'm worried about how it would look and I'd have to re-do it to replace a burned-out bulb.
How can I keep the screw heads for these lights from rusting? Is that just inevitable? Can I replace the originals with galvanized screws or something?
Also, in my pic you can see something that's pretty common on my bus, where the screws holding on the rails have a bit of rust on them. What's the best way to deal with these?