You could just use a credit card as an alternative. Or, when you get to St. Martin there are at least two Banque de France's that I am aware of that should exchange U.S. Dollars to euros for you. One is in Marigot and the other I think is in Grand Case. There's also a currency exchange place in Marigot, but they would most likely take a bigger cut (percentage) than a bank would. Just a few ideas that come to mind.