GB wrote :
I have tracked down the source of a significant leak in my 12 year old Bosch
dishwasher. There's a worn O ring on the water inlet side of things. It's a
fairly chunky O ring about 2 cms wide.

https://i.ebayimg.com/images/g/EzcAA...7j/s-l1600.jpg

Bosch still sell these, but annoyingly they charge around £25 for a set of 4.

Do an Internet search for a local bearing and seal supply company, ring
them with the measurement of the seal and see if they might be able to
match it. If they can, they will be just pence each.