Not cheap new, but Soper might still be worth a quote.
https://www.sytnerstevenagebmwparts.co.uk/p/Bmw__Z4/High-pressure-nozzle--left/132297847/61677057451.html
You could always code out the headlamp wash cycle and block off the tube (if the nozzle is leaking). Or pull the fuse and block off.