Do you have access to a fridge/freezer to store them?
Not exactly the most portable, but what I do is mix chocolate whey, natty PB, flax seed and just enough water to make a thick paste. I then freeze the mixture and it forms sort of a frozen candy bar like product.
It melts but if you can store them in the fridge while at work it should be fine.
It's my favourite pre-bed snack