I don't work for the following company, i just stumbled onto them while looking for a source of perlite and pumice.
Up until recently i'd been getting my pumice from Hamiltons, and my perlite from bunnings.
You can get 100litre bags of grade 4 perlite for 20 dollars
and 25 litre bags of pumice 1mm-7mm for 16 dollars.
much better deal then the 5 litre 10 dollar bags from bunnings.