The U.S. Customs user fee program is the best deal in the Caribbean.  The annual cost is only $27.50  The Decal is available on-line.  You only need a copy of your on-line invoice to show customs when you return - not the actual sticker.  And when filing your eAPIS and you are "warned" to enter your Decal number, simply click on "next" and continue with the filing.  Your submission will be accepted without the Decal number and you will receive a confirmation.