If I can veer off topic for a moment, well only mildly, because this won't help anyone flying UA. When flying on BA out of T5 in a less than premium cabin I always pick up one of the picnic packs from Gordon Ramsay's Plane Food. It never fails to get a comment from my fellow pax as they sit there looking at the swill you get in Y and I'm munching on smoked salmon and the like.

Back on topic, when I lived in SFO I'd pack up my little Japanese bento lunchbox set with tasty morsels made in my own kitchen.