I spotted at least 2 RV doors on ebay the other day, don't remember exactly where but if you search ebay for it you'll come up with some.
I bought a Larson "Secure Elegance" door for my bus. I had a 32" opening and they made the door with that size, it has tempered safety glass w/membrane like a front windshield, and a 2 stage locking system (required to pass DOT specs). Plus it is full glass top to bottom, and the best part is, it's near impossible to break into the bus with this thing!!