Not sure about other locations but perhaps contacting the Tamiya importer for Australia would be good?
HLJ did sell sprues from Tamiya and other Japanese made kits but they have suspended this service following the earthquake and tidal wave in Japan. You might contact them to see if they plan on starting this service up again. It does say temporary on their site, but its been a year now
http://www.hlj.com/helpcenter/partssupport.html