If North Korea has it, so does Iran
Totally true, and would sell it to anyone or any entity that had the cash.
Also, the missile is unnecessary. Build all the non-fissionable elements of the bomb here with off-the-shelf parts, and bribe some 3d world “diplomat” to bring the Pu in through his diplomatic “pouch.”
And to make it even easier, use U-235 and gun-type weapon.
Crude but effective. Ask the people of Hiroshima.