For the folding door try colaw rv in Carthage, Mo they are a salvage/airstreamgraveyard and last spring when we were down there I know I saw folding doors in the airstreams they have lined up like smashed beer cans. Sad to see but a real reminder that towing is serious business. They are very helpful and have a website with their phone number.
Camping world has the drapery hardware you are looking for but bring a visual aid along.
The front lock is a bummer we got parts for ours at Acefogdall in Cedar Falls, IA (Airstream Dealer) but!!!! It didn't quite work, Chris needed to tap it out and he decided to just bite the bullet and buy the whole thing new. SPENDY but we are never going to get rid of the Overlander so there you are.
I'll ask him for sure about the slides as I know we did that too, (when you have a vintage everyone pretty much has to replace all the same things at one time or another) but I think he found what he needed at our little Ace Hardware. Not exactly the same but it does the trick.
Hope you love yours as much as we love ours.