Hi Chris,
The chemical classification situation is like a revolving door. But
you can easily procure ammonium persulphate over the counter in NZ
in small quantities. Just visit your local branch of Jaycar
Electronics who you will find keep stock of it as product CAT. NO.
NC4254 in 400 gram jars for about NZ$15.
Just look at http://www.jaycar.co.nz to find the nearest store and
search on “persulphate” to get an easy result. They, too, no longer
keep ferric chloride.
Mark B
Fourth Axis
http://fourth-axis.com/four-4-jaw-chuck-jwx-30/