They are both used for livestock. Any chance you have some connections with local farmers? They can usually get a lot of these medications from a vet just by calling and asking.
There are some other, more labour intensive options you can use to supplement the medical compounds that may help. One thing you can try adding is to mix bentonite clay with gelatin, raw seaweed (kelp) and the food you normally feed the fish. This has some limited effectiveness by itself but combined with the medication can increase the efficacy of the treatment. The gelatin keeps the clay bound until digested by the fish, and as it passes through the digestive system it helps the fish expel the parasites and also acts to reduce the chances of the parasite attaching.
http://www.allnaturalpetcare.com/DIY...gredients.html
Be careful of some the items mentioned as the difference between a therapeutic dose and a toxic one can be close for some species.
Hope some of this helps.
Charles