Where to buy Furn./Water Htr. screens?

[NMathews]

Hi all,

We have seen and heard of the mesh screens available to cover your furnace and water heater exhaust vents that prevent insects from entering and making nests.

We were wondering where exactly to purchase the right ones for our rig, as I know there are many brands/types of furnaces and water heaters, and plenty of different sizes.

We have a '22 Globetrotter 30', with the Dometic furnace and the Girard On-Demand Water heater if that helps narrow down the proper style.

Thanks!