For me it is Easy to obtain as Scott Stocks it in Canberra

Re the Akadama, I used it mixed with about 20% decomposed Granite as was advised byt the suppliers in Perth. Interesting thought to use it for Reducing growth rates

Also note that other people in Sydney that purchased Akadama in the bulk buy we did, also do not use it anymore.
Note that, I use a 2/3 Diatomite/ 1/3 Zeolite mix so it is not 100%. I agree with Scott, 100% mixes do not perform anywhere near as well as mixed content.
Ken