Have you tried Airstream Supply? If you're going to be somewhere for a while you can order the part(s) from them.
https://airstreamsupply.com/Doors-and-Locks
If the site where you're staying doesn't allow mail/packages, you can see if the local post office will accept "General Delivery". We've had good luck using that, you just go to the PO and pick it up at the front counter.
If you can find the same part at Amazon, see if there's an Amazon Locker for delivery near you. We have also used that for delivery.