REI rents canoes and kayaks for reasonable prices and discounts for members. I would also try local universities, especially if they have an outdoor rec. program or club. I know EWU over here has rentals, so maybe try WWU.
If you've got a military, or military retiree involved, they can rent them very reasonably at the Fort Lewis Northwest Adventure Center (AKA "Outdoor Rec"). Just about any military reservation will have some kind of outdoor recreation rentals.