You make it. I bought the equipment and starters, only cost me $50. Then, I bought full fat goat milk (more tolerable than cow), and I fermented it for 20 hours to get rid of most lactose. It's more runny than cow yogurt, but healthier.
That's what I did for months after I started Paleo, but I have now switched to goat kefir and never looked back to yogurt (and consider that I'm Greek, we live and die with yogurt). Kefir is healthier than yogurt and 5x to 10x more potent. Its bacteria and yeasts actually colonize the human gut, instead of passing through, as it's the case with yogurt. But it has to be home-made for all 40 kinds of microbes to included in the mix (yogurt usually has 3 to 10). The nice thing about kefir is that it doesn't require special equipment, just a glass jar.