vegetarianism and protein

One food not mentioned on that page is quinoa. It's similar in texture to rice or cous cous, and is one of only a few vegetable complete proteins: https://en.wikipedia.org/wiki/Complete_protein

Among the natural sources non processed sources: I would say all the lentils specially bengal gram which has a low glycemic index which will not hurt your "low carb diet" and also red kidney beans which have high fiber.

If you do not mind processed food, then extra firm tofu, the chicken substitutes made from soy especially the ones you get in trader joe's are good. Also, I like seitan which is a wheat based high protein food,