In North America you can get Tsampa from Purple Mountain and from Myers Tsampa. In Europe look out for Sonam's Tsampa, which can be bought in organic shops and drug stores (DM, Rossmann, Coop). It's easily available in German-speaking countries. Remember, Tsampa is whole grains roasted and then ground. It's not RAW barley flour or barley flour that has been roasted. There is a difference in that. Your second option is to get raw whole barley and to prepare tsampa flour from scratch.