Hi Dunsky. You might like to try and contact Pioneer Restorations NZ. The may know the contact details for a Kittyhawk Association (I couldn't find a link but try emailing them for information).
Google couldn't find any specific P-40 Association, but there are plenty of Warbird groups etc, that may be able to assist you.
Good luck
Kerms
http://www.abc.net.au/wa/anzac/air.htm
http://www.pioneeraero.co.nz/