Is there any airsoft stores in Washington?

Legally, nowhere. It is illegal to use airsoft guns, or any device that shoots a projectile, on or in any "public place" in Seattle - which include parks, open spaces, alleys, streets. The police will confiscate your airsoft gun(s). You caould be charged with a crime, or even shot if the cop thinks you have a real gun and he or she freaks out. Sad situation.

Seattle Municipal Code, 12A.14.083

Weapons in public places.A. It is unlawful to knowingly carry or shoot any spring gun, air gun, sling or slingshot in, upon or onto any public place.

B. For purposes of this section, "public place" means an area generally open to the public, regardless of whether it is privately owned, and includes, but is not limited to, streets, sidewalks, bridges, alleys, plazas, parks, parking lots, transit stations, transit vehicles and buildings.

( Ord. 123191 , § 9, 2009; Ord. 119010 § 10, 1998: Ord. 117569 § 123, 1995: Ord. 90047 § 42, 1961.)