Scott, I buy my wine at Discount Liquors which is located in the area of the Belize Yacht Club on the other side of the street. Beer at the distributor but if you get a case at the above it will be only a few dollars more I believe. 10% off on a case of wine.
Diane is correct of course you really should buy your wine at the duty free just before you go into customs at BZE. That will be the best price but the selection is sometimes lacking.
Good luck and have a good trip, it is all good.