Rather hard to arrange from St.John. Branson has granted Gumption's Nature Tours exclusive permission to conduct tours of Necker and even then only when the island is not occupied by paying guest. First you have to get from STJ to Virgin Gorda and right now you would have to go back to ST. Thomas to get a ferry over to Tortola and then Virgin Gorda. Might check the ferry schedule to Virgin Gorda against gumption's schedule and try to find a date that will work.

Travel is fatal to prejudice, bigotry, and narrow-mindedness, and many of our people need it sorely on these accounts. - Mark Twain