Hello and wellcome to the LOC.
Are you sure it is the potentiometer that has gone and not just the link rod that normally fails, the link rod is around £30.00 from a Derby supplier.
Have a look underneath the rear suspension to see if everything is connected.
Lexus only sell the whole thing at a price!!
89407A SENSOR SUB-ASSY, HEIGHT CONTROL, REAR RH 89407‑48030 1 € 387.57