Hello from Colorado and welcome to the vintage Airstream hobby. I have a 1975 Overlander 27 and my son has a 1969 Globetrotter 21'. They are a continual project.
I assume you need an entry door. If the trailer has been without an entry door for very long, the plywood floor will be toast, rotted out like an old log. Used Airstream body parts are hard to come by. You will have to get the word out to salvage yards and see what you can find. It may be the entry door on your trailer is the same as on my son's trailer, and would the the same on all model Airstreams of that vintage. This will make the search a bit easier.
Maybe other will chime in. I see there is a Airstream that a tree fell on that the owner wants hauled away for scrap. Maybe it has a good door.
http://www.airforums.com/forums/f348...am-186978.html
David
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WBCCI #8607 VAC Region 11
KnowledgeBase trailer renovation threads: 69 Globetrotter, 76 Sovereign, 75 Overlander, 66 Trade Wind Such fun !