Physan 20 can be bought from Calwest Orchid Supplies:
http://www.calwesttropical.com/
I would not bother trying to find some Phyton 27, as it is extremely expensive, and not available at most Orchid Suppliers. I have gotten it at Hummert for $53 for 8 oz. It is so expensive that I don't use it regularly and the few times I have, I have not been able to detect any improvement in what ever the probelm was. Fungus spores are one of those ever present things, and the best defense is to grow the palnts with proper culture. Don't mist late in the day, and don't let plants get colder than is normal for them, or give them too much, or too little light, in order of importance. Healthy plants resist fungal infections. I use Physan 20 at a low rate in my fertilizer solution, but again, it is taken on faith that it is doing any good. If you use to much Physan, I can tell you from experience that there will be phytotoxicity, so error on the low side. Cynthia