I don't grow any grain crops but you have the timing about right, Oct to Jan. There are some larger harvest contractors who travel south as the season progresses, particularly in the Eastern States. They are called harvest contractors down here. I did a quick Google search for Australia harvest contractors and got this link for you. I would suggest contacting them:

Australian Grain Harvesters Association

If you want my email is good and I could ask some grain growers that I know.