You don't have to buy anything, the visible rubber of a solenoid doesn't age properly and gets too thin.

Simply replace it with a standard piece of rubber to stick on with glue and the solenoid will work again.

The most difficult is to access this solenoid. But the videos show how to do it. It is useful to take pictures of the screws to be unscrewed to facilitate reassembly. You can have a look at youtube 2dqN6kdqaew or 5-Upb9QnC5Y

It looks like planned obsolescence because it is very difficult to find a rubber that degrades after about 6 years or so. Any standard water tap rubber will last for years!