I recently replaces the license plate light and frame holder on my 1968
Tradewind. I bought mine from Vintage Trailer Supply - Vintage travel trailer parts and supplies!
The light, frame and gasket cost 21.95 and it fit perfectly. I looked and they have the light, frame, and gasket for your year model of Airstream.
Vintagetrailersupply.com has some of the best customer service you will find and I know from experience.
This summer I bought my wife a vintage awning from Vintagetrailersupply for her birthday.... and I mis-measured. I mis-measured by a lot. It was 100% my fault, the awning did not fit and never would and I was sick over my mistake.
I just knew I had made a multi-hundred dollar error and I was prepared to take my medicine. I asked the Vintagetrailersupply.com folks if they could have the factory re-cut my awning down to fit, I would pay the costs for everything plus shipping.
Instead, they cheerfully took my wrong-sized awning back at full costs and then re-ordered and shipped me the new correct size awning.
Geeze Louise, I wa so happy, that is costomer service.
I've since bought hundreds of dollars of supplies from them and have always been happy.
If you need anything for a vintage Airstream, WWW.Vintagetrailersupply.com
would be worth your time checking out.
They are a great group of folks to trade with.