Almonds, Sunflower Seeds, Natty Peanut Butter, Walnuts (all unsalted, no msg.) Fats are your friend at work.
You'd get a moderate amount of protein from those sources (~7-10g per 1/4 cup.) You'd also be consuming a lot of healthy fats which will keep you full for a good portion of the day. There's also amble fiber (~4g per 1/4 cup,) in those items. The more fiber the better.
AND
Since they're low carb (fiber aside,) they will have a negligible impact on your blood sugar while you're sitting down at work (or whatever you do at work,) so you won't be releasing insulin and getting fat while being idle at work. If your job is very active then strike that last bit, they'll just help promote a leaner you!
That's win:win right there.
Throw in a can of tuna or some homemade (no msg,) jerky and you're right for flight my man. Maybe keep a gallon of water at your desk so you stay hydrated as well.
I keep all of those at work with me, sunflower seeds are the cheapest by far, but it's good to have a variety cause it does get boring eating the same thing all day, especially walnuts. And walnuts are so expensive...secret is to go to the cooking aisle at a wholesale warehouse (Sams, BJs,) and get the big bags of almonds and walnuts for cheap. Since I'm rambling at this point I'll end here. Hope it helps.