I have one that's, technically called, an 'accessory'. It's made of vinyl and I, too, have to check it periodically.
Check out this web page on Vinyl Siding Accessories. Home Depot has them. If you don't see it on the shelf, go to the BUilding Materials Desk and ask for a catalogue.
My best to ya and hope this helps.
Jay J -Moderator
PS: Don't think you can use this type of vent for a Power Vent that goes with a Natural Gas Hot Water Heater. In my particular jurisdiction, it would be a code VIOLATION to use this as such ...
© 2016 Renovate Your World LLC