Yamaha CS-15's slider needed

[Gronda Andrea]

Hello, I need  a spare slider for the envelope's attack controlol of my
old Yamaha CS-15.
I've contacted all the  repair centers here in my area that are known to
be specialized  fixing analogue gear, but  they apparently cannot help
me; I've also called Yamaha Italy, but the guy there told me to call the
repair center... they do not directly sell spare parts to a private, and
beyond this  he was very unconfident that there is any chance to get  a
such old part, anywere.
So I wondering if some where in the world, there is someone that still
has these sliders to sell.
Andrea