I've used that for water lilies, iris, etc., in our pond before we moved. I don't if it's where we purchased it (kind of a "high end" nursery) or not, but it's incredibly expensive stuff. I seem to remember a 10lb bag being $30. This was maybe 6 years ago, though, before we moved and, of course, left the pond.
If you needa source for Akadama or something similar, let me know, it's readily available from the many online bonsai sellers, including those on e-bay.
When using these "soil-less" potting media, isn't it difficult to get a nice thick carpet of moss to grow? I've never had any success getting moss established with pumice or other porous media.