Vermiculite is ALMOST as good but you can get perlite pretty much anywhere, including home depot. I'm actually surprised you aren't using it yet- if I'd known that I would have told you ages ago! I think a lot of your problems have been from lack of soil lightener actually; root rot forms in wet heavy soil. It doesn't need to be STERILE, but it needs to be FRIABLE and LIGHT.
Just check the root ball...