You might like trying to track down a San Francisco Pelican, which should be practicable if you have or can develop practice at "scarphing" your plywood sheets to achieve greater lengths. If you find that Tim's suggestions are'nt quite what you need, you could always try to find a used (ready-built) Mirror 10ft 10in. dinghy - over this side of the pond they can be bought for VERY little money!.
Tim is spot-on in his comments about resins. I always use non-solvent epoxy resins (with a heat gun to aid penetration into the fibres of the wood). No solvent means that when it has disappeared, it has sealed the wood and not evaporated!
Hope you have success in your search!