Where would you even find this?

We just received one from a dragon in a campaign to possibly use towards a quest he gave us.

@Infinity_Slayer7 An NPC might drop it for a quest. Alternatively, if you or a member of your party have proficiency in herbalism kits, you can make your own with 4 work weeks worth of work and 10,000 gp (Xanathar's Guide). 

For when you really need get over that post-dragon hangover.....

I found one in a burned-up general store in a secret cache under the floor. 

The dm gave us one of these that showed up as a normal potion of healing with Identify. My friend drank it to heal 10 hp, and then the dm told us what it really was.

Wish spell - a non magic character- and DM - i summoned a superior potion which turned out to be enlarged and expanding potion that was 6 feet tall and 9 feet wide. We popped the top and started to scoop a few bottles full. Lol

This actually gives me an idea for my Legend of Zelda campaign later on lol 

Here's a free fun idea for all of you evil DM's: it's a mimic! One of the best laugh's I've ever had right after the party beat the BBEG and the cleric popped open the Supreme, only to have the mimic drop him unconscious with a surprise attack. The whole table was completely caught off guard!

Got a price for it? 

Trying to be an alchemist's is there any recipes and ingredients.