It's really easy to make at home, for what it's worth. Here's the routine:

1. Take finished kefir and pour it through a strainer. The liquid is kefir, the grains are grains. (You kind of stir it around as it drains; the kefir is made of separate curds and whey but they are easily reunited to make a thick creamy drink.)

2. Take the grains and put them back in your fermenting container. (Nothing fancy; I use a quart bottle.) Add milk to 2/3 full. Cap it, give it a shake, then loosen the cap and sit it on your counter until it's finished. This can take anywhere from 12 hours to a day or two- it depends on a few factors (ambient temperature, how many grains you have vs. how much milk, how sour you like it, etc.) but I don't want to overcomplicate this post too much. Basically, when it separates and there is a layer of whey on the bottom, it's done. Go to step 1.

The kefir can be drunk immediately or added to other finished kefir. I have a gallon bottle in the fridge and I add each new batch to it. When I get too much I strain it to make kefir cheese.

So that's it, really. Add fresh milk to the grains and let it sit on the counter until it's done. Shake, strain, repeat.