The display has got 4 wires, the outer sensor has only 2 (Rocket's) green and brown...
When you start at the sensor's side, the cable can easily be tracked down. It is an additional cable and is routed separately; it is not stuck into a complete wire harness.
Solder a new/used sensor (with some cable length) to the current cable or install it completely into the gauge.
with a minor 600+k