You can almost always find sardines at that asian food market off of Beaverton/Hillsday hwy (the 217 end of it) on the south side of the road.
Although they're usually pretty big.. so you'll want to trim them up good - and for some reason they seem softer than the ones packaged for bait... so i usually cure them a bit (which i do anyways on any of my sardines)
Have you called some of the fish markets down in Astoria. I cant remember the name of the one I buy my sardines from but it is on the docks on Foot and 11th. You can get a box of 50 sardines for $10! They are big sardines too, about 10 inches! One box will hold me for the entire springer season.
The Fish market is called Fergus Mcbairnsie, or something close to that,,,,,,,,or drive over here for the day and just meet a sardine boat at the docks. They start unloading daily at about 4:00 PM. Most skippers will give you a 5 gallon bucket full. I still have sardines from last fall in the freezer, but will use em for crab bait. They are excellent. Better yet, come over for the razor clam dig starting the 24th, and you can pick up the sardines while you are here.