One thing that works really good for me is shrimp. I count out one exact serving of shrimp- which is 80 calories and about 18 grams of protein (Around 11 small-medium shrimp, depending on the brand you buy). I buy the pre-cooked kind so I can have them plain, or just put them on the skillet for a few minutes with a little bit of seasoning.
A tiny bit of shrimp will really fill you up with all that protein! Just make sure you don't eat more than a serving because it is high in cholesterol.