There's a secondhand one on ebay for £16 with postage and Best offer. How cheap do you want it!?
I'd want £30 plus postage and I do have one available. Which I don't think is expensive either.
Or you can get a brand new 3rd party one off ebay from £60. A new Febi from £150 or a new Bosch from £200. I still think that's reasonable.
Are you looking at a new BMW part? That would cost £400-£450 which would look expensive. I don't think many of us on here would go down that route.
Btw welcome to the forum but you really would be better off explaining what your issue is so you can get some more considered help.