Share 'Antibiotics'

One of my chickens was bitten by a mink/weasel/or...... last night. We've seen it and are trying to trap it but still have an injured bird on our hands. She should be ok, is eating and drinking but we are looking for some antibiotics. I don't want to take her to the vet, we just need a round to keep infection away. Any ideas where we could get some?