If there is no severe bearing wear the axles are fine.
You are looking for a spring shop or an online source to replace the tired leaf springs. Basically replacement spring data comes down to width, length and how much weight will be supported. So weighing the trailer and then adding a percentage to that number will get you to the place to start seeking spring replacement. BTW Airstream is sadly lacking data for a trailer of that age. And standards have changed a lot, so invest in a set of springs that will be 20% (give or take) greater load capacity than expected and you will get the height back.
As to replacement parts for seals, bearings. Likely no one alive will have the data you seek for replacements. Again companies close yadda yadda yadda. And going into a parts store and saying I have this year make and model what are the parts? The counter guy is either going to look at you like you have a sickness or ignore you. However tapered roller bearings and double lip seals have been made for decades if not a century. An accurate measuring of the bearings and the seal and you should find one that will work. I got some for a trailer at NAPA store by measurements. It helps if you go at an off time when the counter guy is bored. And www.timken.com
should be a help for you as well.