Does not really help your problem, but I have a Showhauler and needed a replacement basement door. They were able to get it for me, and at what I consider a reasonable price of $400 plus $60 for shipping. Not painted to match, that is my responsibility.
Funny(?) story, but the door opened up while driving down the freeway with a 50 mph headwind, to go with my 70 mph cruising. It flew off and then got ran over. Good thing is did not fly into any vehicle, but it did necessitate getting a new door.
2005 Kenworth Showhauler 45 ft total length
twin screw, 450 hp ISX, 10 speed Ultrashift