Sanwa Supply NT-19UH2BKN2 Programmable Numeric Keypad with Assignment Function, Wired USB Connection, Membrane, 23 Keys + Switch Button

You can assign functions to the standard Japanese 109 keyboard using dedicated software. By switching modes, you can assign functions to all keys except the Enter key, in addition to the four dedicated assignment keys. The assigned functions are stored in the memory of the numeric keypad, so once you set them, you can use the same functions even on computers that do not have the driver installed. The key top covers can be removed, so you can affix stickers with the assigned characters. *Stickers are not included. Uses the same 19mm key pitch as a desktop keyboard.