Myabe the stock of these stores is efected by the area they are in, such as wal-mart or supermarkets where I am dont sell enough Future in this area to make it worth, but the same company in another area such as swanny's area might sell more of it so they keep it on the shelves.
Seems to me the best way is to google Future and check for businesses that sell it in your area, that way you are sure and everyone is happy.
-Jeff