Plant-based sources of Vitamin B-12?

Vitamin B12 is stored in the liver and muscle of animals, and is also passed on to eggs and milk, so these are good sources for non-vegans. Humans produce B12 in the gut, but cannot absorb it. Many other animals produce it in the gut too, so unwashed plants that have been fertilized with animal feces may be a source of B12. However, there are many other reasons to wash your plants before eating them.

Some plants (spirulina, for example) has been touted as a plant-based B12 alternative but is inadequate for most people. As vegans, our best bet is synthesized B12. You can't synthesize it yourself, so no, you can't "grow" it at home, if that's what you mean. Where I live, vegan B12 is available both through the internet and in pharmacies, but I don't know the situation in your country.

The Vegan Society has useful information about B12, as does VeganHealth.org. The Vegan RD has a section about cyanocobalamin versus methylcobalamin if you want to dive into the details.

From wikipedia

"No fungi, plants, or animals (including humans) are capable of producing vitamin B12. Only bacteria and archaea have the enzymes needed for its synthesis."

So you get B-12 by eating bacteria, either dirty food, dirty water, or animals that ate dirty food and dirty water on your behalf.

The "artificial" sources of B12 come from large vats of bacteria.

I don't have the source handy, but there Korean Buddhist nuns at vegan for decades at at time, without trouble, the possibly sources would be the bacteria on the fermented cabbage, or maybe the bacteria on the seaweed sheets, or some other source in traditional temple cooking.

You'd think that with probiotics and fermented foods being so popular at the moment, there would be some research into if any of those culinary versions have B-12.