Call your county extension agent or your state vet. They may know of a vet who will prescribe. Be aware that it is against federal regulations to prescribe baytril for an entire flock, expecially a flock kept as livestock versus pets. Tylan injectible is supposed to be better than powder.
Are you saying your friend always gives tylan in the water? That is not a good thing. Antibiotics should not be a constant, but only a treatment for an indicated period of time. Hopefully I misunderstood.
As to the receptionist who laughed, I would lodge a strong complaint with both the office manager and the veterinarian. People keep many different species of pets, and many people have distinct dislikes of certain types. If she disliked cats would that justify her laughing at having someone's pet cat treated? Ditto for if she disliked dogs, or parakeets, or parrots, or hedgehogs, or ...
And if it is livestock rather than pets, it is equally unjustifiable--livestock are income, and keeping a flock healthy is as important as is calling in the repairman when manufacturing equipment breaks. How would that receptionist feel if the copier or computer repair person laughed at her when she called in to have them fixed? Or the xray machine, or any of the other myriad pieces of veterinary technology used at that clinic?