Cheese sandwiches. With peanut butter rather than real butter. Also jam and vegemite are not temperature sensitive. I would question the health of muesli bars - how much sugar is in them? Hard boiled eggs (not shelled until just before eating) are pretty good for protein too and will go one day easily without refrigeration. Trail mix (make your own) is a good non-temp sensitive munch to fill gaps. Snap peas are a nice crunch snack when you get bored with carrot sticks. And there is always popcorn.