You can purchase a SCOBY from specialized fermentation retailers, general online marketplaces, or local health stores.

A "kombucha mushroom" is the common name for a (Symbiotic Culture of Bacteria and Yeast). While it looks like a rubbery, tan disk or "mushroom," it is actually a cellulose pellicle that houses the active cultures needed to ferment tea into kombucha. Where to Buy a Kombucha Mushroom (SCOBY)