Where does one buy the media from?

I used Walnut shell, I tried quite a few pet shops, but none had any. Reading some reptile forums it seems there is a bit of controversy about it choking some type of pythons or something - I did not laugh too much  as I'm sure some would ridicule our interest in pins.

Gun shops had some media - which went under brand names, but seemed to be either corn cob or walnut shell, but it was REALLY expensive, about $20 for a box of similar size to a tub of butter - would have cost a fortune to fill my tumbler.  I filled it about 2/3 to 3/4 full and added a few teaspoons of turtle wax car polish to the mix.

Ended up buying from these folk  http://www.wellwood.com.au/walshell.htm

tut tut, not a sponsor of the site, but I mention it because I reckon the real value of this site is in sharing tips, tricks and info among enthusiasts.  I ended up with a huge bag - more than I suspect I'll get through in a lifetime so if anyone wants some pm me and it's yours for the cost of postage and a beer for my troubles, which is $15 for an Aust post 3kg sachet.