I eat turkeysandwiches every day for lunch. I buy mine from my grocery store's prepared food section. They bake and marinate whole turkey breasts daily, and you can just have them slice it for you.
I personally would stay away from anything with preservatives/nitrates. That stuff can't be good for you. I'd look for something where the ingredients are more like: turkey, water, salt, and maybe some spices.
Also, even at the deli counter, you can see or ask to see the list of ingredients on those rolls of "meat".