I work night shifts although not 12's, mine are 9's. I actually lose weight on those shifts because I find it hard to fit in enough quality calories during my day. Protein bars (not 'energy' bars which are no different calorically and macros same as chocolate bars), sturdy veggies prepped and in a baggie in your pocket ie baby carrots, celery, cauliflower/broccoli florets, jicama sticks, lo fat/sodium jerky or salami sticks in a baggie, low fat cheese cut into sticks or premeasured wedges ie Laughing Cow or Babybel, HB eggs kept in their shells in a baggie until you need them. If you have a spot at your station, try a shaker bottle and a packet or measure of protein smoothie powder in a baggie. Takes a moment to mix & shake up, then you can drink it down, or leave it at your station and take a swig every time you check in there. Also at your station you could bring single serving Greek yogourt for protein and an apple, cut up orange wedges, fresh berries, etc. All of the above are fine without refrigeration for your full shift. The eggs must stay in the shells til you use them though.
Good luck.