We visited Buenos Aires last summer and bought some bottles of Malbec wine at a store near St. Martin park. This is very close to the pier, less than 5' by taxi. I do not remember the name of the street because it was our travel agent who took us there, but I think it was on a corner, right in front of this beautiful park.
I believe the name of the store was WINERY SHOP.
Why don't you just put a bottle in your suitcase at home and take it with you. All suitcase are placed in your room usually within a hour or two after boarding, have done it my self and had no problems your suitcases are delivered and so are your drinks