Is it just the 3" Perko (or Sea Dog) cowl vent? They're all over the internet and new/used chandleries... though you might have to buy the deck ring with it. I might have a spare cowl somewhere. I replaced the forward vent with a deck plate - but I seem to recall that the deck ring didn't come out in one piece. If I get around to it this year, I might replace both the engine room vents with dorade boxes. Or maybe try to build the boxes and re-use the vents.