After some googling I discovered that zeolite is used in hydropnoics and also in some pool filters. So I googled pool companies for Bunbury and sure enough
bunbury pools and spa mart have zeolite. Admittedly they only had 4 bags left atm . BUT the guy said he'll get it in happily for anyone who wants it. just over $23 for 15kg. A few more dollars than Perth cost but not a lot. I've bought 2 and left 2 so if you are around Bunbury and chasing some they had 2 bags left today. ( only open til 1 on Sat , I'm guessing normal work hours during the week. )