You need Nystatin and/or ketoconazole or fluconazole, all will need to be ordered.I can't seem to find any internal fungicide for livestock anywhere. Not even for cattle or goats. Will food grade copper sulfate work?
For Nystatin, search for Medistatin.
For ketoconazole, search for ketoconazole for fish.
For fluconazole, search for fluconazole for fish.