Fortunately, there are a lot of alternatives and recently in our neighborhood a place called Starfruit opened up. Their frozen treats are made from Kefir, a "probiotic dairy beverage." Kind of like yogurt, kind of not, but tummy friendly. It's a little more sour in nature, and quite honestly not a favorite drink of choice for me. But in frozen form? Not so bad. The selection of fresh fruit toppings at Starfruit are amazing and the pomegranate flavored frozen kefir is both tart and delicious.
I don't know if you'd necessarily come a running to Starfruit if lactose wasn't your enemy, but it has proved to be a tasty cold treat that feels at least a little healthy.