After a few requests regarding making couplers in 1:64, 1:48 & 1:24 scales, I've finally gotten around to this job, and have made them available in plastics, metal plastics & raw brass/bronze.
They can be found at https://www.shapeways.com/shops/kiwitrains?section=NZR+Couplers&s=0
I've gone with 2 designs suited to accommodate a variety of materials. The faces will need sanding down for instance.