The only one I'm aware of is a CSA with Healthy Family Farms, an organic farm in Santa Paula. Their CSA includes a herd share, and gives you access to their dairy products (primarily goat, but they make cow's milk & butter available too): milk, cheese, ice cream, yogurt, and kefir. They sell via local farmer's markets – let me know where you are and I can tell you which market is closest to you!