System Three is the best Epoxy out there for your needs. They are also a local company. You can't buy direct from them any longer, but Fiberlay in Ballard has the complete product line and all the tools, cloth, and safety gear you will need.

On Marine Grade Ply, Dunn Lumber was the only company I could find in Seattle that was willing to order in a single sheet of 1/2 14 feet long for the bottom of my drift boat. They get it from a company in Oregon. You can graft two 8 foot sheets together if you have the right clamps, but I wouldn't try it!