My DD absolutely LOVES puffed corn! I get it from the health food section at Safeway, it has nothing added to it at all so I don't feel bad if she eats a container of it when we are out. We call it popcorn and she thinks it is a great treat :-D
Actually I get lots of things from the helath food section as easy to pack snacks, another favourite of DD's is the little packets of Boost fruit balls. Oh yeah and the Rice Rounds biscuits.