There is a special cleaner which you can use forget name but if that is your preferable solution I will find out. It is the only type that will not damage the electric sensors.
Second option is supplier of new ones. I located a supplier on line who sold me a new one with warranty for my Mercedes for £22.00 + postage. My Mercedes guy scoffed at it and said it would never work. One from Mercedes is £365 + Vat. Guess who is laughing now, 5 minute fitments and better than the factory one.