Disposable respirators in the modern style showed up in the 1970s, and the N95 standard everyone is now familiar with for unrelated reasons came out in 1995. Why does anyone have black lung?

Prescriptions via telehealth are pretty common in the USA, and while people do sometimes request antibiotics for dumb reasons, OP’s reason isn’t.

I’m sure it’s hard to get drugs people use recreationally that way, or something extremely risky, but not something common and low-risk like amoxicillin. You can just mail order that as long as it’s marked for use in fish tanks.