Below is the picture of a Tail Light from a 40s model Airstream.

Most of the time folks are looking for the Lens
( some times called a Cake Light)
and when they find it on eBay it is usually brittle.

This light and Lens are No Longer Available (NLA)
But there are some Reproductions around at VTS.

The best light replacement we have found is using one of the following
lights. You will need to seal the old holes and place this new light
over the old location which will cover it up. In other words
our two replacements lights will cover the old space
completely.
Please Note, your old fixture may have had a flange.
You will not need the flange for either of the lights below
unless you need to use something to fill in the space in
the body of the trailer where the old light went.

 

In LED

 

This product is Available on our sister site.

Click here to see it.

 

If you don't want an LED we have a Incandescent.

Pictured below

 

This product is Available on our sister site.

Click here to see it.