shrinking models is not so easy as thickness of material is an issue. might be worth while contacting tebee (Tom Bell) as he has done a lot of 3D models, including Gn15. Nothing as small as N scale, but worth asking.
Z(6.5mm) is not the only gauge suitable for narrow gauge, consider T gauge (3mm gauge) to create something minimum/miniature
Narrow gauge Francophile interested in 1m, 60cm,50cm , 40cm and smaller gauges . Build in scales from 1/6th to 1/24th. Also 1/32nd and 1/35th using 16.5mm track to represent 50cm and 60cm gauges. http://www.rue-d-etropal.com