DD,
As it has been said so many times, the RV industry is starving. I bought my doors (already framed) from Kinro for less than half of retail. Call them directly.
http://www.kinro.com/index.htm
I bought brackets from a Truck salvage yard and put 1/4 inch sheet steel for a floor. then I built a frame with square tubing. give Kinro the inside dimensions of the opening and they will build the doors to whatever you need. my generator and air conditioner are in these compartments, so I got vented doors.
Doc Weaver