I mentioned it before, but I prepare my bento food on Sunday for a week. (bento making tips)
I went to a Japanese grocery store yesterday and got Okara (leftover soy pulp from tofu making)
It's really cheap and rich in protein, calcium and fiber. I often used it as a substitute of meat,
-Okara shu-mai (vegetarian)
-Okara vege burger (vegan)
-Okara "meat" ball (vegan)
I pickled veges and am ready for another week of bento making!