Here you can buy a complete system that is technically fully functional and visually even in better condition than its counterpart at the Computer History Museum in Palo Alto (I was there last year).
+ NeXT Cube Workstation with installed NeXTStep on Harddrive
+ NeXT power cable
+ NeXT cube monitor connection cable
+ NeXT Monitor (Frog Design)
+ NeXT keyboard
+ NeXT mouse
Find some pictures here:
https://www.ebay-kleinanzeigen.de/s-anzeige/next-cube-komplettes-system-in-museumsqualitaet/779797819-228-9293Please make a reasonable bid.
I would be very happy to sell in person, but shipping is possible.
Merry Christmas :)