Komachibu is a small round form of yakifu, grilled and dried fu. Fu is a traditional Japanese form of wheat gluten, that is a good vegan protein source. (Read more about fu_.) If you like to use seitan, you'll probably like _fu as well. Komachibu is available at any reasonably stocked Japanese grocery store (in the dried food section).
Komachibu are about the size of a large coin. When they are reconstituted in water, they swell up to about the size of a small scallop (they do shrink back down a bit when cooked with this method). The texture is very soft, like very very tender scallops. I don't pretend that they are as good as real, fresh scallops of course, but if you've given up shellfish for dietary reasons, these are not bad at all. And, they are terrific in a bento box, vegan or not.