I strongly doubt NK has the capability to produce these weapons. I believe they are being supplied by other countries, either officially & secretly or by a rouge element.
How are they transported without being detected? Even if NK is somehow manufacturing these weapons where is the radioactive materiel coming from and how has it avoided detection?
They are making their own plutonium. They have a breeder reactor set up for just this purpose.
North Korea can mine uranium in their own country. They can produce plutonium in multiple nuclear reactors. Apparently they also have a program to produce highly enriched uranium.
“how has it avoided detection?”
While uranium is detectable from 10s of miles away...perhaps even low orbit sats, plutonium for weapons is not detectable from across the street.
Men on subs regularly get within 5 feet of the stuff.
Modern weapons are made from mostly plutonium and Norklandia produces their own in their reactor.
Bill Clinton ensured this course.