IIRC, the last person to individually book a tour to North Korea decided to shirk his appointment with the state ministry in charge of chaperones and took advantage of the fact that a Trans-Siberian railway crossing was listed as a valid port of entry on the standard tourist visa... it's not often you get to play with (if only mentally now) the technicalities of international transit. It makes you grin like hell.
And you can only go as part of a set tour which is usually over a week. So no weekend tours and certainly not by yourself.