A drum swap meet is being held on July 17 at Alexander Park in Chehalis Washington. That is about halfway between Seattle and Portland.
The organizers seem to be cymbal guys, bringing 100-ish hand made cymbals imported recently from Turkey. They will also have other cymbal brands.
Other than those guys it's whatever everybody else brings. I saw the ad just now on craigslist Seattle. The ad states it is a drumforum.org event.
I found the event on drumforum site
It looks like the place to be on July 17