I don't know about in NZ, but Fibremaster in Australia have a few of the old Group C body kits for various Mazda's, those flares look identical to the ones on the Findlay RX-3.
http://www.fibremaster.com.au/mazda.htm
MAX3FL-201 Flares - Group C. $420.00
MAX3FS-202 Front spoiler with brake scoops - Group C. $180.00
I'd love to see any more pics of that RX-3 as well, what a great looking car.