We use St. Brendan's Isle, a mail forwarding service in Florida. We use them in lieu of USPS as an online mail service for all our mail both in the USA and St. Thomas. If you move around a lot or on an irregular schedule, USPS can't keep up very well. They will ship items to St. Thomas from you directly or a third party that you may purchase something from such as amazon.
https://www.sbimailservice.com/