where can I get antibiotics for my feral cats...help please

I have a colony of ferals I feed and care for. Yes, I know there is a forum for feral cats but thought this might give me a wider response.

Occasionally they get in scuffs and get scratches. I give them doses of antibiotics in their food as needed to clear up infection\swelling.

So I go to both of my regular vets to try to buy more antibiotic but now I'm told "we can't sell you any without seeing the cat"! Right...I explained I needed help and which is better..to have them suffer and maybe die of infection. Of course they did say " sorry"..ha!

All about the money I'm sure. These are both vets I support with thousands every year for my own house rescues...go figure.

So does anybody have any suggestions on antibiotic to use? Suggestions on sources?

Just hate to see the cats suffer but those of you that tnr know re-trapping is almost impossible.

Thanks in advance.

you can buy antibiotics for fish at the pet store