Agricultural antibiotics. You can get five ounce bags of terramycin and others, intended for bees and pigs, but work just fine on people with infections.
And one of those little pocket scales, or a reloading balance.
Major meltdown means no FDA.
A great source of penicillin is actually aquarium supply stores. I can’t remember the exact name, but it is pretty close to clinical doses and safe.
What are the contraindications to terramycin?
How long do they last, remain usable?