Hey Marcingo, I just picked some up at the Rock Hound shop in Victoria ,so you should be able to get it at place that sells tumbling supplies .
They will sell small 2ounce packs for $ 1.55 or pretty nearly any amount you want.
I am going to try it for removing hardwater marks from a tank ,nothingelse seems to move it . Sounds like a good tip.
Thanks Kronk
.....................Dave