I don't know anything about those drugs, but the most common thing in the States is to give a combo of Baytril and doxycycline. The vet should be able to prescribe a Baytril suspension--even if they don't have the ability to mix the proper dosage there, they should certainly be able to send it in to a pharmacy and ship it to you. (Are you in the States or the UK?)
ETA: And to answer your question about taking both in together but being charged for both--I'm assuming you only needed one looked at, and you just took the other for company? If that's the case, there is absolutely no reason why you should be charged for two exams. With the vet's refusal to prescribe Baytril, and them charging you twice for just one patient, I'd strongly suggest finding a different vet.
ETA: And to answer your question about taking both in together but being charged for both--I'm assuming you only needed one looked at, and you just took the other for company? If that's the case, there is absolutely no reason why you should be charged for two exams. With the vet's refusal to prescribe Baytril, and them charging you twice for just one patient, I'd strongly suggest finding a different vet.