Yay, I've tracked down a supplier in this corner of the world.
Kudos Petroleum is in Gisbourne, New Zealand but he's happy to post to Australia. I asked for prices and he emailed back with:
Hello Bill
201 is $81.83 excl GST for 3.85l
306 engine oil $36.49 excl GST for 3.85l
Regards
Kevin
021 736 544
GST is 12.5% and his email address is
amps.electronics@xtra.co.nz
Please note the prices are in Kiwi dollars, so after the conversion it's almost free.