I've been considering switching to the metal ones, but would probably paint
them also. The outside kitchen fan vent cover has also begun to deteriorate but I've not discovered any metal replacements.
Good point about using paint particularly made for plastic. Maybe even one of the small cans used for painting
models would work. The kitchen vent cover isn't yet as bad as the roof vents, so perhaps paint might save it.
I've looked at that style vent and saw them on a Casita
at a rally
. Esthetically, they didn't look right to me. The scale somehow seemed too large for the front location on a Casita. I actually had one in my hands at an RV repair shop and it seemed like it would be very functional. The design has been around for years, made of sheet metal and used on fireplace chimneys which are subjected to strong prevailing winds.
Thanks for your ideas,
& Ann K.