I am not aware of where you can get bhavchi - the botanical name of the plant is psoralea corylifolia, and it is grows in plenty almost all over Asia, particularly in India. If you live in one of these countries you should have no trouble obtaining the plant or its extracts - the roots, seeds, and leaves are available mostly in powdered form and should almost certainly be found at any Ayurvedic store if nowhere else. The plant also goes by the names bakhni, babchi, bukchi, and bawachi, so perhaps you can try asking for it by these names.
If you live in another part of the world it might be more difficult to get your hands on bhavchi, but today Ayurvedic products are available all over the world, and in addition, you also have many Internet sites that sell all kinds of products. As a last resort, if it is absolutely imperative that you obtain bhavchi, you could ask someone visiting Asia to get some for you.
In all frankness, there is no known cure for vitiligo (leukoderma) - many herbal remedies are recommended, but none of them has proven to be effective. Still, leukoderma is not a dangerous disease, so there is no harm in trying something different.
answered by G M