Le Grand Marche has yacht provisioning services.

TTOL sponsor Shop and Drop has regular grocery deliveries and I think has also started a yacht provisioning business, but you should check with her.

If you have time to do it yourself, Grand Marche, link above, is probably the closest large grocery store to Oyster Pond, although there are not really any large grocery stores really close to OP. You don't really need a liquor store per se, in SXM, as the grocery stores all have large liquor departments. There are a bunch of liquor stores downtown, but you don't really want to have to deal with one of those, as it would be a hassle with traffic and parking.

Cash and Carry is a standalone liquor store in Cole Bay, and has some of the lowest prices on liquor, but they don't have as good a selection as Grand Marche. Don't know if they have delivery or not. (Despite the name, Cash and Carry accepts credit cards..)