The former would be a limited supply with a shelf life (even modern antibiotics go bad after a few years). The latter— synthesizing penicillin is no easy task. Even if I knew how - which I absolutely do not - it’s among the more difficult things in the world of biochemistry. It’s why Alexander Flemming earned a Nobel prize for it.

And basic penicillin is nothing compared to the antibiotics we have today.

Additionally, I’m not really very cool with altering the timeline