Malcolm models the South Australian Railways in N scale and uses 3D modelling to produce models. In the past some of the models were used as masters and released as kits by Aust-N-Rail and Peter Boorman's Workshop. Now that Peter has retired from the N Scale casting scene, many of the models were made available from Shapeways under Malky's N Scale Models at the Shapeways shop: https://www.shapeways.com/shops/malky-s-n-scale-models
Some of the models have now also been made available from alternative sources:
Rob Carpenter's Aust-N-Rail: Aust-N-Rail - HCA cement hopper, 8300 brakevan
and Geoff Biggs' Dogspike N Scale Models: Dogspike N Scale Trains - Redhens, Jumbos, Superchook, Steel cars
These two suppliers use resin printers which can produce a very good surface finish, as well as finer details than previously possible. Their versions of the kits will include some added details such as handrails, steps and similar which previously had to be etched brass. The Shapeways option will remain open for the foreseeable future.
Instruction sheets for these models are available here:
HO Scale Model Instructions
Decals and Custom Etched Brass Parts
Decals and, where applicable, custom etched brass parts are available to complete these models, as well as some extra decals for Peter Boorman's Workshop kits.
A listing is available here: Decal and Etched Parts List