Update: As others have mentioned below, PM10 works also. wow!
Just came across an old Ozbargain deal - https://www.ozbargain.com.au/node/200758
Tried the "PM5" code for the matrix protein and to my surprise, it still worked!
5kg with $7 flat shipping for $120.05 total. Not bad.
Out of interest i tried entering a few other PMxx numbers. There is a PM10 discount that worked for me.