A couple of smaller stores to try:
Marmot Mountain Works, Bellevue -- I've bought a few pairs of boots here.
Feathered Friends, Seattle -- known for their down bags, jackets, etc., but I bought a pair of plastic boots there many moons ago. Worth checking out.
Pro Mountain Sports, Seattle -- never been, but owned by Jim Nelson, co-author of the "Selected Climbs in the Cascades" guide books; good reputation.
HTH.