Hey Tom,
I do have one spare lens which I need. I've seen other early sixties
models with replacment taillight lenses, slightly different but close enough.
The best replacement I've seen is a Signal-Stat tail light (trucker type)
with a chrome cover ring. It is bright, it fits, available at most truck
supply stores and most importantly, it looks very "Airstream". Tom Howarth
replaced his Flying Cloud tail lights with those trucker type and they
look very good. What else do you need?
Bill