Really depends on what type of flying people are going to do. As in the type of operation and which company. The difference between a F100 and a c172 operation...
The chopper company you are referring to is Heli Niugini. They use to produce a fantastic book that has all the maps cut into A4 or reduced to fit A4. Not sure if they still produce the book. You should also remember that even if they do produce the book the maps are still the same maps from the 60s and let me assure you things have changed. Digicel towers have been erected, roads have been built etc.
The above book only works really if you know where you are going. Regardless of what some people think PNG experience is worth its weight in gold.
Again depending on your operation another publication you may require is Bill Percels strip guide.
The RAAF stuff is virtually useless & out of date but a good start.
Air Services Limited do amendments
They are just not like Australia
they are available from briefing... Once again experience is
Jepps plates are available however you need to buy the whole of South East Asia package to get PNG. And not all procedure / approaches are in Jepps e.g. Hoskins. Also a point to note is the Jepps are just reproduced Air Services charts therefore if a DME step takes you into a hill on those charts so will the Jepps e.g. Buka
Something about PNG experience again
The official CASA PNG buildings are not easy to explain. Best place to obtain your charts & maps is from your employer. Hopefully you get a training captain with experience and do yourself a favour write down all the hints he gives you if you get a "specialist" direct entry command guy... good luck
Lots of people cannot believe the state of Airservices & CASA in PNG but it is the way it is...