Hi jpconte,
Thank you for using the Support Forum. The cartridges are no longer available from Xerox. Please consider searching on the part number 8R7881 for compatible cartridges or remanufactured cartridges from authorized Xerox agents or dealers.
Are printer cartridges 8R7881 for the WorkCentre XK50cx available anywhere? If not, is there a compatible cartridge I can buy, or do I have to use a refill kit to inject my old cartridge with black ink?