The Principality of Zeon Emergency Rations come 10 cans to a box and can be ordered online here through Premium Bandai.
Specifically, you can buy Principality of Zeon Emergency Rations.
This grounding of the narrative in human psychology has given the Gundam franchise a remarkably complex in-anime social structure, the latest effect of which is that you now can buy Gundam emergency rations in the real world.
That said, the Zeon Emergency Rations really do have an incredibly long shelf life, as they’ll keep for up to five years.