I believe the well known auction/bidding site has a seller in Oz.
They don't seem to be listing right now, but perhaps they will re-list in the next few weeks, so perhaps keep an eye out.
Or could you :
Find a "reshipper" with a US office.
Order from a US ".com" marketplace, eg south american river website
Use the reshipper's US address when ordering on the marketplace.
The reshipper receives the package, then forwards to you.
If the reshipper needs an invoice for customs declaration, then print it from the ecommerce site as a pdf.
To find a reshipper, search for "cross border shipping company".
Check the reshipper is willing to ship the item you want, since they may have a list of prohibited items.
Try to find one that will ship the required item.