Strange. I've seen those doors in RV dealers showrooms. Maybe drive around your area stopping in anywhere they sell RV parts. Even boat shops sometimes carry RV parts. I once found an entire rear tail light assembly for a '94 Bounder in one. Mine was all rusted out.
Then of course it might be they're trying to order the door the same color as yours so they don't have to pay for painting it. That's likely what's going on. You could call some of the salvage yards on
this list and check if they have your color in stock. Of course not all salvage yards will allow that or pretend they're too busy to check colors but many don't mind checking and pulling a part of a certain color. I assume you're able to take a digital picture of your RV and upload it to a salvage yard's email for color matching.
There are 3,000 or so salvage yards in the US, you might even be close to one. Then there are many car salvage yards that have scores of RVs sitting there but aren't on the RV salvage list so drive by them too, see what they have.
If you find one, demand the shop buy it and have it painted if need be.
Good luck.