Dimattina Coffee in Osborne Park carry Pullman tampers (which I think I can recommend ;)) but not sure if theyre open Saturday. Epic Espresso in West Perth also do but are officially only open on Saturday for classes.
Your best best is probably JavaB here on Coffeesnobs who is our Production Supervisor and based in WA and (without knowing his plans for tomorrow!) Im sure hed be happy to suit you up with one. You can reach him at enquiries[at]coffeetamper[dot]com[dot]au.