How do we apply for a Travel Permit for our son?

Hello. My wife is Chinese. I am Australian. Our Son (2 years old) was born in China. We live in China. I have a resident's visa. My son has an Australian passport. We will travel to Australia during December & January 2012/2013. My son will leave China on an Exit Permit. Friends in the same situation have previously been provided with a Travel Permit, valid for two years and multiple entries and exits to China.
Many thanks.