Friends of Kim. This is about Alejandro and the Korean Friends Association, by Micromovies. You probably want to skip to 3:10.
North Korean Labor Camps, a Vice documentary about NKorean workers in Russia.
The Game of Their Lives, a BBC Four production about the 1966 NKorean football team.
Crossing the Line is about Joseph Dresnok, and American soldier who defected to North Korea in 1962. It has a very annoying soundtrack and incorrectly describes the country as "ruled by one man." BBC Four again.
Vice Travel's Inside North Korea. Haven't seen it - watching now.
I'll add to this later. You'll find millions of Korean War documentaries, too.