A big welcome to the forums. Wow, you've got some nice toys!
I don't know anything about Airstreams in Australia or shipping to Australia, but I'm sure there are sources out there. I have seen a couple of resellers shipping vintage Airstreams to the European market. If you are thinking of buying new, you might consider talking to
Airstream Corporate in Jackson Center, OH. I see they have a link for Australia but I couldn't find a dealer listed, so you might have to give them a call.