Soo.. I have been following this thread.. From an RV Parts Guy...
NONE of the manufacturers will talk to you for parts without a VIN, even if you are a parts person. Jayco is the most lenient of them, and easiest to work with IMO. The reason is not to keep your camper "OEM", but its to narrow down the part number for the EXACT item that was on the camper. The database has millions of parts. To get to one light fixture, off of a camper, that was built in a certain year, without a VIN is almost impossible.
To solve this, if you do see something on a camper that you like and want to incorporate it, you need the last 8 of the VIN for a parts search. Like LilBigfoot stated, its not impossible, Talk to Jayco, or a Jayco parts rep, and just explain what you are doing. I don't think you will get a hassle from anyone. If you do get a run around, shoot me a PM.. I will get the part number for you.