Great question.
My fave veggie tasty low carb work snacks, all easy as long as you plan in advance:
A few cashews or other nuts
Olives
Slices of avocado, or even guacamole with chilli and lime
Chunks of coconut
Tomatoes
Beetroot
Radishes
Plain Greek yoghurt
Sticks of carrots, cucumber or peppers with dips like humous, tzatzki, baba ganoush, or broad bean and mint.
Make a small pot of salad - e.g. Spinach with a boiled egg, mozerella tomatoes and basil, or a coleslaw made of red cabbage, grated carrots and mayo.