I did exactly what you are trying to do right before I traded my 2011 23SS. I was able to get a door under warranty and had it shipped truck freight. I needed to pick it up at the Yellow Freight terminal in my area. Since it was warranty, I traded the labor cost to install for the shipping and did it myself. (took me about 2 hours, reused all the hardware and brackets) But that was a warranty claim.
This was around Thanksgiving... Fast forward to the following season, first week of April, new TT, maiden voyage, stop for traffic on a exit ramp, rear ended by honda accord... Progressive insurance claims adjuster comes to my house following the weekend and I explain I would rather make the repair on my own with OEM parts (needed bumper, some aluminum skirting, a spare tire bracket, roof ladder and the plastic rear valance). Insurance gave me actual delivered parts cost plus standard labor rates. (made out nicely on the deal!) Bought the parts directly from Forest River with a credit card and they shipped direct. Had the items within two weeks.
Each division of Forest River has a parts person that covers certain styles and models. You can find the appropriate person here Forest River RV Contact Us - Forest River, Inc.
I would start by informing them that you are not satisfied with the services offered by any of the local dealers and would like to purchase the replacement bunk door directly. Be sure to include your VIN will all emails. That being said, if you were to contact them with a specific list of needed items, in a professional manner, and make it as easy as possible with photos and details - I think you will be successful.
2014 Rockwood Ultralight 8312SS Diamond Edition
2011 F150 Super Crew 4x4 5.0L - Traded!
2016 F350 Lariat Ultimate Super Duty Crew Cab 4X4
Northern NJ - God Bless America!