Why not try one of the Greek bareboat chartering companies. If you boat is reasonably new (not more than five years old), you shoud normally not encounter any problems entering a contract under their management. For a start, I suggest you contact people at the following website:
http://www.athenian-yachts.gr/
In the contrary, older yachts are hard to charter and you would rather have to skipper and look after them yourself, thus offering different than bareboat services.
Good luck and happy ending