I'm restoring a 22 ft. 73 Argosy and there are 2 vent pipes that come up through the roof which, after 42 years, apparently became brittle and the tops are busted off. I've removed them and now have a bare black plastic pipe sticking up with a piece of screening over them to keep out the bugs. Since the tops are all busted up, I don't know what they originally looked like. I'm assuming they weren't solid plastic, otherwise the vent pipes couldn't "breathe". Anybody know where I might find suitable replacements?