I go to the Vineyard quite often. It's such a beautiful place.
I haven't found any real B&Ms there. There are some places that do sell a good selection of cigars. My first stop is always Trader Fred's at the Triangle in Edgartown. Fred has a relationship with Carlito and usually has a good stock of Fuentes including Opus X, VSG and ESG. All are fairly priced. The prices aren't marked, but they will give you a price list if you ask before going into the small walkin. It's a fun place to poke around, lots clothing and sporting goods.
Jim's Package in Oak Bluffs has a small walk in humidor. The selection seems to be getting smaller every time I visit, but I often go in the off-season so maybe there is a better selection in the summer.
Our Market on the harbor in Oak Bluffs has a couple large cabinets of cigars. They always have a good selection with some high end stuff like Davidoffs. Good beer and wine selection and a small food mart.
For me there is nothing better than walking the beach with a good cigar and my sweet wife.