I don't know the part number sorry. But when I was hunting for a replacement cable all I could find was a new top half (button power), fortunately that was the half I needed.

There's quite a few speedo cables on ebay, would've thought all models would share the same gearbox and tachometer connections to be honest.

The black box you talk of is the speed sensor for a trip computer. if you find a cable it'll fit both with and without that speed sensor - no difference.