Valve for KH Director

[vitmark]

Hello!
Where can I buy a new valve for KH Director?
The tube that the valve presses has worn out. There was a hole where valve push tube.
I noticed it only after about 30 days. As a result, the plastic valve body completely dissolved by reagent, and the valve irrevocably rusted.
I made tests all working, exept valve.
It's happened after 2 years use, two times in a day.

Vitaliy.