SIM card with data for unlocked iphone

I'll be staying in Maho for a week and need a prepaid data voice sim card for my iphone. I haven't been to the island in a couple years. Can anyone suggest a good reliable quick place to get a sim card with a prepaid plan? Thanks.

Sharon, the Queen of SXM, sells Chippie sim cards. Her store is located in the strip of shops on the first floor of the Royal Palm.