Welcome to the great world of Airstream Renos...
it should be a great project for you and your son - if you have patience to wait for the parts - half the fun will be hunting them down.
Speaking of which another new member housebg - just posted - and in their post they mention someone that he just bought parts off - from a wrecked Airstream - maybe it is your lucky day? Or better still that housebg was spared in their accident to make a new friend in Airstreaming.
You could send them a PM to see if you can get more info on the trailer they mention.
I also saw a "parts" trailer recently on e-bay - but just looked and the door is missing too - why it might even be the trailer you just bought
Good luck with your reno.