You can make you own "greek" yogurt by straining plain yogurt. I remember people posting it on the lowcarbfriends website when I used to do Atkins. I've never tried it because I never quite cared for Greek yogurt but I hope you can use these instructions.
3. Straining the Whey
More potentially good news for low-carbers: It turns out that most of the lactose in milk and yogurt is in the whey. Furthermore, it is easy to strain much of the whey out of yogurt, and at least one company, FAGE, sells strained Greek-style yogurt. To strain the whey out of yogurt yourself, put a coffee filter in a strainer or colander and put that over a bowl in the refrigerator overnight. What will be left is sometimes called “yogurt cheese,” which has a consistency that can reach the thickness of soft cream cheese if enough whey drains off. This can be eaten any way you want or mixed with other ingredients for foods such as dips. How many carb grams can you deduct for straining? There's no really great way to tell for sure, but FAGE Classic Greek yogurt claims it has 6 grams of carb for a 7-oz. serving. Another advantage to straining yogurt is that the concentrated yogurt has more protein per cup.
For the complete article I found through internet search:
Yogurt on a Low Carb Diet - Counting the Carbs in Yogurt