It COULD be done by shipping only people/brains, machine tools, designs and process knowledge to Norklandia.
That way nobody sees major components in shipment.
I once saw somebody on Internet who claimed that there was a private jet(Gulfstream type) taking off Pyongyang and its destination was Moscow. That was from one of those sites tracking the flight of commercial airplanes. I checked immediately and it was indeed on their screen at that moment. That was intriguing. I wondered who were in that flight.