Thanks for that suggestion RO...it is exactly how my own mind was working! However, an apparently knowledgeable person I have already explored the idea with in NZ claims that the "Japanese-made" Leaf is significantly different from other varieties, even having differences in wiring looms, colour coding, plug type and other basic technical aspects, with respect to the wiring. If this is correct, it would seem to preclude the possibility of simply swapping the dashboard components.
Do you think such a difference is likely? It's reassuring to know that replacement units, such as the Ebay one you referred me to, are available, even though the cost in NZ$ would be a significant addition to the recent car cost. However, in the long term, it would probably pay off in increased convenience, providing such a unit could be made to work in the New Zealand environment.