According to this and many other sites, kombucha extract/drink is rich in B12:

Kombucha Mushroom (part lichen, part bacteria and part yeast), which is not actually a mushroom but a large, flat, pancake shaped fungus-like growth which is part lichen (a moss), part bacterium xylinum, and part natural yeast growing together. When placed in a mixture of sugar water and tea for 7 to 10 days the kombucha produces a wine-like health restoring tea and a new baby kombucha. The beverage is rich in glucuronic acid (which stops the progression of viral infections), hyaluronic acid (strengthening connective tissues), chondroitin sulfate (found in cartilage), mucoitin-sulfuric acid (a normal chemical found in the lining of the stomach), vitamins like B1 (thiamine), B2 (riboflavin), B3 (niacin), B6 (pyridoxine), B12, folic acid, lactic acid, dextrogyral and usnic acid which possesses strong antibacterial and antiviral effects.

http://www.happyherbalist.com/analysis_of_kombucha.htm