At my job I never know if I'll get an actual lunch break or not, it just depends on how the day is going, so I try to pack a few things to keep me going untill I can get home or get a chance to eat a real meal. I also keep a few basics (mayonnaise, cheese, deli meat) in the break room fridge.
Try stuffing celery with cream cheese mixed with some worcestershire sauce and green onions. It's so yummy and the cream cheese helps to really fill you up. Keeping a little baggie of nuts in your purse helps too, for whenever you really can't sit down to eat at all.
Cream cheese on some deli ham is good, or swiss cheese on turkey. Just roll it up and eat
Hope that helps.