Last winter, I think it was, someplace within TF, someone was talking about 3D printing these. I know it's not much to go on, but they are out there - Good luck
I’ve looked high and low for these for a couple of years now. If someone comes across a reliable source I could use a few of these myself.
I’ve looked at current offerings made from stainless steel but they all have mounting holes drilled in them. I’d prefer to 4200/5200 them on.
Trying to find the one in the attached picture too…
There's no real need to use the same style of cover unless you want to match others on the boat or it's some sort of "classic" that you want to maintain in original condition.
West Marine and other boat retailers have stainless steel vent covers that attach with two or three small screws. Easy-peasy.
#5 post: I made one at my last haul out to replace one that was lost. Use one of the remaining ones as a mold, using glass cloth and epoxy. Came out close and at the waterline its difficult tell that they are different. Used 3m 4200 to attach.