If I can help you out shipping parts to Australia, let me know. I'll do it for cost.
It's not cheap though, the USPS raised prices a few years ago.
https://ircalc.usps.com/?country=10013
Priority Mail International® Large Flat Rate Box
USPS-Produced Box: 23-11/16" x 11-3/4" x 3" or 12" x 12" x 5-1/2"
Maximum weight 20 pounds.
$95.95
Priority Mail International® Medium Flat Rate Box
USPS-Produced Box: 13-5/8" x 11-7/8" x 3-3/8" or 11" x 8-1/2" x 5-1/2"
Maximum weight 20 pounds.
$75.95
Priority Mail International® Small Flat Rate Box
USPS-Produced Box: 8-5/8" x 5-3/8" x 1-5/8"
Maximum weight 4 pounds.
$34.95