Not sure of this fits your Usecase, but bringing some kind of precooked stew to work might fit it. Some sort of lentil stew could work, as you have both protein and fibre. If you need something readymade you can buy at a store, then it could be something highly preprocessed like protein bars and such, which I would nod advise to have in your diet all the time.

Back in the days before "The Incident"(tm) when I was a regular at the office I often had one of those whole-meal-shakes like Plenny/Joylent which covers both protein and fibre and doesn't take much time to make. But tbh: Having a proper meal with colleagues is important and can be good for your psychological well-being. If you are the weird shake-gulper this might work less good. ;)

Roasted Chickpeas? Not sure how they score on fiber but I assume not so bad

Dried Edamame.

Edit: There is some unsaturated fats now that I remember. Also, try to get low sodium ones. Read the nutrition facts when you get the chance, but I am certain there's a good amt of protien and fiber. Very portable, can be eaten like chips.

I make peanut butter oat bars, small, dense, tasty. Only an issue if you have allergies or diverticulitis etc.

Most kind of seed, like Flaxseed. However eating raw seed is super dry. I try to mix it with low fat yoghurt and/or add a fruit like Dates for a bit of sweetness

Do you have a refrigerator at work?