If an RV salvage yard doesn't have what you need, this place will make a screen door to whatever size you need: All-Rite Screen Door - Entry Doors
I have no idea what the cost might be.
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2008 Fun Finder 189 FBR, (replaced by) 1996 Shasta 265DBFW April 2017.
2006 Jeep Liberty 3.7 (replaced by.....)
2006 Chevy 2500HD, Duramax, crew cab
It's a big world...explore it!!!