Believe the biggest and best attended by suppliers is the Oakland in the Water
Show. It's usually in April so you'll have to wait a while for it.
Seattle has a boat show
in January. Haven't attended that show and don't know how well it's attended by vendors. Believe it's a much bigger show than the one in September.
There is also the Wooden Boat Show
in Port Townsend, WA, September 5-8. Aimed more at maintenance/building wooden boats but has some general marine
vendors. It's a neat show to go to just to see all the old and new woodies.