This is Midwesterner’s wife. I actually wrote a lengthy column in the Yated about making it yourself. I gave a recipe for homemade yogurt, but you may use storebought if you wish.
I have not found a cholov Yisroel brand of Greek yogurt, so I wrote how to make it yourself.
The way to do it is to strain regular yogurt. You strain it either by using cheesecloth and having the yogurt strain for a few hours in the fridge over a bowl. Or you can line a colander with several coffee filters, also placed over a bowl for a few hours in the fridge. It comes out delicious! If you overstrain it, you will end up with yogurt cheese. You can always add the strained whey in the bowl back into the yogurt to thin it out again. It’s worth the effort, especially if you make it yourself! When I make it from homemade yogurt, it tastes like sour cream.
I hope that helps.