How do you get Moo Moo Milk in the base game(not expansions)?

I won an Auction for Moo Moo Milk and the NPC was saying they'll hold onto the item like I'll get to return with the money later. I come back after selling PokeBalls and Full Restores but cannot interact the right way! I don't play games for the realism! Let's add a way to get Moo Moo Milk for people buying the game! Plus making such a change would look good on NASDAQ! It gives 100Hp! I haven't seen any other classic items missing in the game like this nor heard of any others that are missed.

Please address this.

To Games Freak

From,

Eremas