There are so many ways to eat beans and lentils and there are a large variety. How are you eating them?
You might want to try different ways such as hummus, roasted chickpeas, split pea soup, lentil soup, black bean burgers, etc.
Also, all plant foods contain a mix of the two types of fiber so you can certainly fill up on vegetables for a low calorie fiber boost but I personally eat beans daily so I'm a fan.
Fiber 1 is the best high fiber cereal I've found, but not sure about it's sodium or even what you think is low sodium. Beans and eggwhites sounds gross to me, and I don't mind beans - I'd find a new recipe! At least add some salsa to that or something!
If you are looking for a breakfast type dish, well its not necessarily breakfast but you might want to try chickpea crepes. Chickpea flour is ground chickpeas, you can find it in any Indian market but also places like Whole Foods or even Amazon has it.