I used to feel that there wasn't anything available. The obvious option is a packed lunch, but failing this is there a supermarket near by; you could go to the cooked meat section for choices of chicken, bacon ribs, sausages. Alternatively I have noticed 150 g of yogurt (Yeo Valley for example), which would go great with a 3 sector blueberry, raspberry and strawberry punnet with some plain mixed nuts - for a bit a decadence some dark chocolate squares. Another option is some deli cheese to go with either of the 2 aforementioned.
Just takes a little planning where you can mix up different choices for different days,. You may have some envious feelings towards colleagues with their crisps, sandwiches etc, but much of these convenience foods are not that healthy.