Try this bloke brett.drysdale@bigpond.com he might be able to help you out - or point you in the right direction. You can always place your details on the Aussie Grain Harvesters web page agha.org.au Put your post on the "harvest talk" section.
Ask mr O`Keeffe from the Ohio state uni. intern program. He got me the adress for a rural job agent in Perth. They have a lot of harvesting jobs starting in November