The Australian agency is the resource, Garrett stopped selling to Australians from Overseas for some time now.
Many many years ago, I paid a total A$500 including shipping, for 2x ACE 250's delivered to me in 3 days, just by ordering from the USA.
Price in Australia was over $500 each ACE 250.
Australian Dealers need to make money too, but there was just too much difference in cost and retail to ignore at the time.
My Google fu is greater than yours... good luck, maybe look for a secondhand coil, but I have seen some cheap Garrett bits float up from a Dealer on Gumtree occasionally. Maybe Australian Ebay or even Amazon ?
https://www.garrettaustralia.com.au/