Can i just check something with you, you are asking about DC IN power cable harness. I assume you mean for the DC Mains inlet jack. This is not seperate, on the NL50MU the DC IN Jack socket is actually part of the mainboard itself.
6‑43‑NL5MU‑020‑1N is a Cable that links the LAN PCB to the Mainboard
6‑43‑NL5MU‑021‑1N is not listed as a part for the NL50MU at all.
What was the source for these part numbers as i am not sure these are what you looking for and dont want to price and order the wrong thing for you