Chlorhexidine is basically an antiseptic. That's mostly what you want, something you squirt on that kills everything. Because it's on their feet it gets dirty fast. Most of the things you would put on a cut for a human will work here. Just keep in mind that a rabbit will lick it and a human knows not to. So whatever it is should not be poisonous or should go away in some fashion before you put the rabbit away. For instance hydrogen peroxide is not good to drink but by the time you are done cleaning it's dried and gone so the rabbit won't poison himself if he licks it. Neosporin is an ointment that it's ok for them to lick. Try to think about treating a cut on your own foot. Worst case, soapy water is better than nothing right? What you have available will vary, but the concept is the same, clean it and try to keep it clean.