Airstream running gear replacement parts are NOT like the automotive parts. Especially when dealing with models that are decades old. Airstream made running changes when parts ran out.
So getting what you want (Especially outside of the states) is a little different than knowing year make and model.
version likely had lug studs and not lug nuts. The brake magnets are likely round and this design has been replaced with oval magnets.
Unless you have to have exact copy, following the recommendation above is a good start. Get a "loaded" backing plates. (One that has the shoes/magnets and mechanicals attached) And a drum/hub (with bearings) of the correct diameter. (I believe that to be a 12" drum. If the new drum has studs in it you will need new lug nuts. And frankly it will be easier with studs and lug nuts.
In the states these can be generic parts from a good trailer store. As they are readily available and are not that complex. Auto Safety House LLC ¬Ľ Parts
This is one from Phoenix.