The answer to this question depends on what kind of kombucha product you are looking for. You can usually buy tea, which people drink for its properties of detoxification and liver health, at health food stores. Other products, including powdered tea and capsules and concentrated tinctures, can be found at some health food stores or through online vendors. If you wish to keep your own kombucha culture at home, which will provide you with fresh tea daily, you will need to obtain a starter culture.
Kombucha is a symbiotic culture of acetic acid bacteria and yeast, or "SCOBY," that produces a fermented tea when fed with regular black or green tea and sugar. Traditionally, people obtain starter cultures from friends with their own colonies. If you don't know anyone with kombucha cultures, however, you may be able to find someone in your area who can provide you with some, or you can purchase a starter culture and supplies from an online vendor. It costs next to nothing for someone with a kombucha colony to make new colonies and provide starter cultures, so many people are happy to give them away for free or for the cost of shipping. Even if a fee is charged, it is likely to be little in comparison to the nearly endless amounts of tea the culture can provide you with.
Once you obtain a starter culture, you will also need a large glass jar, a small piece of fabric and a rubber band to cover the jar, tea, and sugar, all of which are easy to find at your local grocery or convenience store. No special kinds of tea or sugar are required — any kind of black or green tea you like and plain white sugar will suffice. Kombucha is easy to make and maintain, and whoever you get your starter culture from can likely provide you with instructions. Alternatively, many methods are described in detail in innumerable Internet sources.
Once you have a healthy colony, you can have a steady supply of tea, start new cultures, and share them with your friends. A colony does not last forever, but by using cuttings from the mother culture to make new, young colonies, you can make your own fresh kombucha tea indefinitely.