I have found another on-line source for Airstream/Argosy parts.
It is called Out-of-Doors Mart. They are located in North Carolina and claim
to be the oldest Airstream dealership/service facility in the world.
Their online parts store is at http://www.odmrv.com . I found some "J-Trim"
there, which I have not been able to find anywhere else.
They told me that they have a lot of stuff that isn't yet in the web store
yet (they are adding new stuff every week) so if you are looking for
something in particular just give them a call or e-mail.
I have no connection to this company except as a satisfied customer. Your
mileage may vary....
Dave