You need a governers palace on Honghr to build them. However, I can tell you from experience that Noghri are glitched at the moment and don't shoot, so they're basically useless.

Also you have to leave vader on the planet for a while

@Ben Okay interesting. I think the mod might benefit not only by fixing that bug, but also switching what building creates them. I would never have guessed that the income building would do that.

@Brooks - I totes did. The Noghri Leader said they were with the Empire but I had no new units and saw no means of producing them through the normal methods.