The best source of information would be the CAA website but with the exception of Waiouru I am not aware of any Charts for Ohakune, Raetihi or Karioi. If your planning to land at Ohakune then it would be advised to contact the Big Red Ski Shed in Ohakune as they operate a flightseeing operation from that private Airfield. Raetihi I know the guy who owns the land its on but Wanganui Aeroworks might be the best place to seek landing permission? Karioi not had any dealings with that field I am afraid. If your wanting field information then those people I mentioned are your contacts.
As for Waiouru, well that belongs to the Army and to be honest I have never seen any aircraft land there or been given permission?
Charl once published a map on that Microsoft Flight Simmers forum requesting this kind of information showing Google Earth plots of all the strips in the Central Plateau. Most of them are just unmarked Paddocks used by crop dusters, google Earth is unreliable with its information as some of these plotted strips have fences running through them after the owners of the land have re-sectioned fields.
I have a chart for this area which unfortuantely due to copyright I will not be willing to copy. Best again to contact the usual suppliers to get those charts.
When you get down here dudduddud look us up, would be willing to give you a guided tour of the area
