Wow, your very lucky to have to have the correct tail light. I was also lucky enough to find one for myself and Frosty plus 2 NOS lenses but i doubt i will find any more. And you have an Answer muffler too...cool.
I would have thought all NZ models 82-84 would have head that tail light too as they pretty much got the same bikes as us, but maybe they didnt? Only other countries that got that tail light are South Africa, Belgium, France and UK and probably a few countries like Finland etc.