You might be able to ask at one of the dive shops that are going out to the Blue Hole if they could drop at one of the Atolls on their way out and arrange for them to pick you up a couple of days later on their next trip. They don't always go on a regular basis out there especially during the slow season. You might also try Frenchie's on Caye Caulker, Frenchie has some property out near the Blue Hole and a large enough boat you could hire. I'm sure that it would be quite expensive since gas costs are high.