Its Protrack here. I have just joined the Forum with a new R3 underway from the US. It should be here early next month.
Convincingly, all members have pointed you out as the Forum's Centre pillar and main person to talk to about overwriting the US database to the NZ version.
Are you still able to convert and install into a USA purchased R3 the NZ speed camera database? If that is the case, I would proceed purchasing a US unit and make contact. What will your costs be for this service?