I have bought and used kefir grains from this site:
www.culturesforhealth.com/starter-cultures/kefir-cultures.html You can make it with coconut milk too!! (
www.culturesforhealth.com/coconut-milk-kefir-recipe) They have a lot of articles on that site to help you with making it. It's really easy, you just have to keep up with it, but if you are drinking a small amount daily, it isn't hard.
The kefir that you take you abx with isn't doing you any good though. The abx kills off the good bacteria as soon as the abx dissolve. It's best to wait for 2 hours after taking your abx to take any probiotic. It's my understanding that by then the abx have left the stomach and are far enough ahead of the probiotics that the probiotics then can replenish the good bacteria without the abx killing it off immediately.