Check First Rays, - he is a member of this forum, with a vendor page. He has Phyton, Physan, and other chemicals.
I use a little Zertol, a commercial grade concentrated hydrogen peroxide, at a low dose (read the label). Zertol is 30% active peroxide, where hydrogen peroxide from the local pharmacy is only 3%. Diluted properly, it is very safe for the plants, can be used as a drench. It is more prophylactic, rather than attacking a specific disease. Leaves the air with a "fresh, just after the thunderstorm scent".
First Rays has Zertol available.