Since you are in Seattle, there is a place in LaConner that will build you one if they don't already have what you need.
www.boathardtop.com Boaters Discount Center......Directions by Boat:
They are located in the Swinomish Channel. They are between the two marinas. They are about 100 feet north of the fuel dock.
Directions by Car:
If you are traveling on I-5, you need to take the Highway 20 exit. Head west on Highway 20 until you reach La Conner Whitney Rd. There will be a stop light, a Farmhouse restuarant, and a gas station at this intersection. Head South on La Conner Witney Rd. At the end of this road, you will enter a round-about into La Conner. After taking Morris st. through town, turn right and head north on 3rd st. Take a left on Dunlap, and you will run into our store.