You may like meuseli in yogurt, given your current choices.
Dried fruits, nuts, large flake oats, other cereal grains .. Mix and store dry as a big batch.
Dump yogurt into a resueable container, top with generous serving of meuseli, cover, put in backback. Eat within 3 hrs for best results.
This is like the steel cut oats &yogurt suggestion, just even tastier in my opinion.
Try making yogurt yourself too, especially if you like it tangy, which is easiest style to make. It costs the same as milk that way. Way less than $2 per quart.
Google both for basic recipes.