A prn would be a pill, not an injection. Prn means take as needed. There are a few antipsychotic meds that would work for this, but you should talk to a doctor to pick one. But it sounds like you need more than a prn, probably a regular daily dose, with maybe a prn for breakthrough symptoms. You will probably need to be stabilized in hospital, or at least with very frequent pdoc appointments if you are staying at home.

I think going on your trip is a dangerous idea. Hang in there, you will get stable and out of psychosis, but you need medical attention to get better. This is a serious illness.