I recently ordered some Walker Bay parts from inflatableboatparts.com. I selected USPS Priority as the cheapest delivery option. Arrived in 2 days, and the USPS boxes fit into our "large size" USPS-approved mailbox, so the (rural) mail lady din't have to pull into the driveway and honk.
Not that we don't love our Mr. Brown. He's always prompt, cheerful, and brings biscuits for the dog.