Hard boiled eggs. Salad (green salad).
If you’re into sandwiches, cold cuts will do ok without refrigeration for a few hours.
@canidmajor is right – Kind bars are great. I like the kind without chocolate, but if you’re into chocolate, they have it with chocolate, too. I like the cranberry almond one and the coconut almond one.
Anything will be ok in an office environment without refrigeration for a few hours. As long as it’s not “outside” temps, meaning 80 and above in summertime, and doesn’t have mayo on it, cold cuts, pasta salad with Italian dressing, hard boiled eggs, etc. will all be ok from morning to lunch time if kept on your desk.