you could start your own from tea, but it's like a 4 week or more wait. So you have to worry about mold and bugs. :/
There are a few places online you can get them that are reputable, but it's best if you know someone who has one themselves.
As far as drinking with fillings - not a problem from what I understand. I asked the doctor and he was actually pretty amazed I even knew what Kombucha was, because that was either a "hippie" thing or something mostly the Russian and Bulgarian community do.
I apparently continue to amaze them.