Bring a few picks down with you and ask someone to make you one based on the plastic model. I haven't seen them being sold, but someone should be able to figure out how to make one. I would assume the pick would be made out of conch. They are a few guys/gals on the island who shave conch into jewelry, shouldn't be that hard for them to make you a pick.
Check with Carlos at his shop in front of Hicaco Tours most every day starting at 4pm. He specializes in silver, but has lots of conch pieces too. He can point you in the right direction if not make it himself.