There is a new shop in the arrivals section of the airport so you can purchase bottles when you arrive. (Haven't seen it for myself yet) I think you're only allowed one bottle per person?
Oh that's right, duh. I purchased there upon my last trip down - $22 for Tanqueray. It's that one store just before you go through customs. I had to declare the bottle. I don't know how many bottles you can purchase but I noticed some people purchasing a few (3) or less.