Have you tried Amazon?
Havoc, this is coming. They are slowly making it harder to buy antibiotics off the shelf to use as "preventives". It may seem painful initially in the short run, but the scary part is antibiotic resistance is a pretty tough challenge. Many commercial growers simply try to avoid infections in the first place with biosecurity measures, so they do not need to feed preventive antibiotics.
To me, the scariest part of it is for humans. I read a story last week that a type of bacteria, resistant to even the "antibiotic of last resort", was documented in the US. It has appeared in other countries, but I think it said it showed up in a culture from a woman with a UTI. This sort of thing has the potential to change all sorts of things from a common cut to surgeries.