Have you contacted UPS? They are an international shipper. They should hopefully have information on dealing with customs.
Otherwise, I used to pick up fish from the Delta hub here. Delta is international, but you might have to deal with customs yourself. Australia I believe also has some very strict laws when it comes to the importation of fish and animals. You need to make sure that whatever you are wanting to ship is even legal. Then it is all going to be really expensive.
Your best bet would be to contact an importer/exporter and find out their process.