I have to second the telestial option....in fact I'd give the owner (Ken) a call. He is incredibly well versed in international mobile communication options...I've known him for 2 years now as a customer.
If you still want to pickup a local SIM...on your way to the cruise ship (if going by taxi or some other means that you have some control over), have them stop at a Dixon's..they are as numerous as Radio Shacks or a good sized news agent would also probably have them for multiple providers.