You might be able to work something out with Ralph Packer. He owns the marine
railway next to MV shipyard. Have you talked to the guys at G&B? Perhaps they have room behind the Tisbury marketplace where you can set up. You can also try giving Russ Wendt a call. He has his own boat hauling business.
Packers might be easiest as you won't have to unstep your mast
Goodluck, I grew up on the island and know how absurd the prices are down there.