I am not particularly familiar with that area and where you might find an Airstream dealer. Did a quick google search and none appears to be in the area you are traveling. Found a couple of RV dealers.... might see if they can help you out... or maybe you can get supplies and make the repairs yourself. It will rain, hey, it is the Northwest!
Vacationland RV Sales
1400 Iowa St.
Bellingham, WA (360) 734-5112
7060 Enterprise Road
Ferndale, WA (360) 384-0456
There are a number of different RV dealers listed in British Columbia that are near there...
Good luck finding something! There is a Airstream dealer in Eugene, Oregon about a day's drive south of you.
Mrs. NorCal Bambi traveling in S Tardis ~ from the Great State of Jefferson
See my new blog on my little town: Yreka History