I believe that the traditional gift for a person's 21st b-day is enough alcohol to make them respect the substance for the rest of their natural lives. Now, that said, I'm just going to take a stab in the dark and say "you're not 21 yet, are you?" My parents were actually pretty cool about friends' 21st b-days so long as they could supervise, and you might try that route. Specifically, so long as we consumed it in their house, so they could monitor who was driving and who wasn't 21 yet, they were fine with providing alcohold for someone who was no longer a minor at my expense. Just a thought.