Kokoda is one of the great (difficult!) established walks of the world. We got a strong endorsement for the lead guiding company from one of our Aussie contributors who joined one of their tours in 2006.
That company is Kokoda Trail Adventures.
The Kokoda Trail is one of the world’s great treks, linking the southern and northern coast of Papua New Guinea, it is a challenge to be enjoyed by the fit bushwalker. …
The 96 km Kokoda trail passes through rugged mountainous country of rainforest, jungles of fern, orchids, birds and clean mountain streams which tumble into steep valleys.
The unspoilt villages throughout the Kokoda Track will welcome you and the Koiari and Orokaiva people will greet you with smiles and tempt you with seasonal fruit and vegetables.
Visit Kokoda and enjoy the adventure of your lifetime.
It’s tough, even if you have porters carry your packs.
But it’s popular. Kokoda guided only 24 hikers in 2000. But in 2006 they led 850. (more stats)
It may be time to start planning a trip to PNG. No independent hiking is allowed, so far as we know.
hikers and guides at the Isurava Monument
besthike.com 
DO YOU KNOW OF ANY GOOD INDEPENDENT GUIDES TO LEAD A SMALL GROUP OF FRIENDS, ON THE KOKODA TRAIL. WE DON’T WANT TO DO A TOUR.
Sorry John.
I do not know of any. Likely, but not certainly, you could arrange that in PNG.