Thanks for the advice, Pete's MH.
After having no luck with the Camping World OEM guy, I called Challenger Doors myself. I spoke with the sales rep for my region (https://www.challengerdoor.com/
). She asked me to send an email with a photo of the sticker from the inside of my door. I had it and sent it. She said I would get a quote the next day. I waited a couple more days and heard back from the CW guy who got me a quote of $96 +shipping. I ordered it.
A couple of days later, I got a quote from Challenger: $66.
They are gettable from Challenger Door. Mine was a one-off situation where I was having the work done by my fiberglass guy, but I imagine if I had been in need of more serious body work and more doors, the body shop would have built all of this into the process and I'd have never known where the doors came from.
My advice is to take photos of any of the stickers inside your coach. Without that, I would have been SOL.