Protein bars, etc are not "good" proteins. Most are prepackaged junk and come loaded with salt, sugar and carbs which are not high-density. You want food sources that feed your body without spiking your insulin. Also, stay away from processed foods (especially meats) because of excess sugars, salt, nitrites/nitrates, etc.
Here are natural high protein sources which will satiate you and help build/retain muscle:
- greek yogurt (non-sweetened, or lightly done with Stevia if you "must" have)
- hard cheeses (cheddars, swiss, parmesan, etc)
- cottage cheese
- nuts like almonds, walnuts, pistachios (also have the "good" monounsaturated fats)
- chickpeas (hummus for snack dip)
- beans (red, navy, kidney, etc ...)
- chicken
- eggs
- beef
- port
- fish
If you're sensitive to kidney stone issues, you'll want to stay away from those sources which have high oxalates; somewhat narrows the list above.