Check out Maine Cat
- they have 30 and 41' cats for charter in Hopetown, Bahamas. Not exactly what you are looking for in terms of the length of the cruise
, but they might make you a deal.
One other point besides the hurricane
season is you might want to just fly to the Bahamas instead of having to make two crossings of the Gulf Stream
. That way you can spend more time enjoying the trip and not worrying about crossing what can be a nasty piece of water