Not sure off hand but try contacting the store called "Provisions" 508-228-3258 they might be able to guide you.
This answer is coming rather late... The Grand Union market which is a matter of a few yards from the Boat Basin has all of the bottled water, soda and mixers that you are likely to need. They are okay with yachties "borrowing" a shopping cart to bring things out to their boats on the docks. If you forget to bring the cart back the dock attendents at the Boat Basin will bring them back for you but you really should do it yourself.
For booze, call Murray's on Main Street (508-228-0071) and you can make arrangements for deliveries. If they are busy they probably are not going to respond positively to a request for one bottle of Grey Goose but if you have a good sized order and can be flexible on delivery times they will work with you.