Most functional components on Airstreams are not Airstream-specific. We have a local RV parts store in Phoenix where one can buy nearly all electrical, plumbing and mechanical hardware parts (except those dang, funky Swedish, swing-out, cabinet door hinges -- where the heck did Airstream find those?).
What we can't find at Al's RV, we can usually find at West Marine, down the street. In fact, marine parts stores carry a lot of stainless steel parts that were designed for saltwater use. So, if you can get past their high cost, these parts look great on Airstreams and will last forever.
Here's a sample link to a connector on West Marine's Web site:
MARINCO Inlet at West Marine
I don't know exactly which cover you broke, but you can probably find it on one of these two sites. Then, you can look on www.amazon.com
to see if you can find a better price.