Give Machacha Charters a call - not b/c of that whole mako in the striper tourney thing, but b/c he is a good guy and good fisherman.
They run out of edgartown. They're a six-pack, but I bet they have a 2nd boat to work with.
Consider the ride to Menemsha where the Vanderhoops charter out of. West Basin on the Lobsterville side to be more specific. Tomahawk Charters run by legendary Native American guide Buddy Vanderhoop will get you on the happy hunting grounds faster than just about any other boat. If he and his brother Chip are not already booked they are two of the best charter guys you could ever hope for. Buddy has put more clients into 50's and 60's than anyone else on the island...especially during the Derby.
Lookup Captain Chris Peters - he got that world record Mako a few years ago on the Oak Bluffs Monster Shark Tourney - he does pretty good in bass too...