As Grumpy noted, Camco. They make several sizes of screens for RV furnaces. If you have a newer Jayco, you may also have an Atwood AFM/AFS/AFL series furnace, and the cover may not be available in stores yet. The other day I stopped by our local Camping World store and picked up a set of screens for the Dometic refrigerator on our new 23RLSW, too.
TV 2010 Ford F-150 Supercab
TT 2016 Jay Feather 23RLSW