M.P.
You can find greek yogurt everywhere. I buy it at Kroger, so any grocery store just next to where you find the regular yogurt..... Each yogurt can/may have different amount of sugar, it is good to read the label. During my 2nd pregnancy I had Gestational Diabetes and I was able to consume 30g of carbs per meal as my Nutritionist recomendations, it is important that the carbs come more from fiber than sugars. You will find the information on the labels.
Hope that helps.