Pumice: where do I find it?

[Asian Cymbidium Empress]

I only use the traditional Japanese Cymbidium Mix that is composed of 3 kinds of pumices: hard kanuma, baked akadama, and satsuma. I buy them as a premixed bag in a premixed ration. Of course, all 3 grades (large, medium, and small). I only start growing Cymbidium goeringii after I was able to find them. Unfortunately, it is not available in North America (Us/Canada), so I flew to Japan to get them.

FYI: There are different qualities of the pumice and you only want to use the best one. The poor quality ones will break down very fast and the pot can be water logged.