Hello Janusz --
The part numbers for the keyboard rubber contacts are:
VU328401 KEYBOARD RUBBER CONTACT CT 2M 12KEYS
VU328501 KEYBOARD RUBBER CONTACT C' 2M 1KEY
The "1KEY" contact is for the high C.
Hope this helps -- pj
P.S. I recommend getting a copy of the S950 Service Manual because the key/contact mechanism is a little complex.