When you say full canvas are you talking about the enclosure canvas stuff with the eisenglass windows and such? If so, I would say your best bet is getting something custom made by a canvas shop. Even if you were to "buy" a used set, they are all custom fitted to the boats at the factory so it more than likely wouldn't fit either way.
You are going to pay money to get one custom made but that's probably you're only option. Other option is just to drop the price a little and not offer the full canvas enclosure. Let the next guy worry about it.