You can now purchase electrodes directly in Australia from Practitioners Supplies
Here is the US to Australian conversion:

Model
879100
895220
895240
895340
896350
901220
901240
SN2020
SN2040
Model    US size 
1.25" round
2x2"        
2x3.5"  
3x4" 
3x5"                 
2x2" sensitive 
1.5x3.5" sensitive  
2x2" snap
2x4" snap
Australian size
3.2cm round
5x5cm
5x9cm
7.5x10cm
RTI
5x5cm Pt Blue
4x9cm Pt Blue
RTI
RTI