Not sure if this is up to date, likely not, but these are the locations listed for the Top Up Machine. As I stated, in March, The Mailbox was useless and both Dutch side locations at the UTS stores were not working.

The Reloadable TopUp Cards are available at:

The Mail Box, Simpson bay

Trendy Cosmetics/Cell Phones, Back Street #68, Philipsburg

UTS Store (in Philipsburg)

UTS Store (in Cole Bay)

Dutch Delight (Princess Juliana Int Airport)

Tech Hub (Le Grand Mache (Bush road at the Roundabout)