Probably your best bet tbh. Mine split so had to buy from dealer. Was £22 6 years ago. For all the hose and connections from the washer bottle to the jets.
Messaged an ebay seller in Lancs that is breaking a load of Z4', but will also give BMW a buzz tomorrow to see what they can do.
Anyone got a part number?
I have one you can have for £12 posted, took it off my E85 pre-facelift when I fitted aerodynamic bumper without headlamp washers. Pipe to each washer are present and pipe has been cut-off where it attaches to main washer pipe. Here are pictures showing pipe and cut end, let me know if you want it -