I bought my Vitakraft Yogurt drops at Petsmart. They are the same brand as the ones for hamsters and such but they have different ones for dogs. Here is a link:
Vitakraft Drops Dog Treats - Treats & Biscuits - Dog - PetSmart
If you look toward the bottom it says: Available in three flavors: Yogurt, Peanut, and ChocoMilk.
As for the yogurt -- I would try not to use the low fat.