Kokoda Track

My husband and his dad want to trek Kokoda and want to know if you can book treks on the ground or are you best to book prior to getting there? What are the best trekking companies and can it be done on a budget?

If you haven't already, try the PNG tourism website: http://www.pngtourism.org.pg/ActivitiesEvents/kokodatrail.htm
It has a list of Kokoda Track operators and their sites, and some background info. It's a start...