Ben you could try these guys (ebay store in the US), I got mine through them a while back and by the looks of the receipt I dug up they cost me $244 US posted. At the time I think the conversion was pretty good for me, dunno if its that good now. But in Australia expect anywhere from $600 up IIRC.
http://stores.shop.ebay.com.au/Sparkplugssource
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