Pella Casement window lock plastic cover

Hi,

I have a pella casement window that has a white plastic sleeve that slips over the metal lock to lock and unlock the window. The plastic sleeve has come off and was accidentally thrown out. The window locks and unlocks fine but is missing the piece of plastic over it which matches all of the other windows in the bedroom and kitchen. How do I go about replacing the piece of white plastic that slides over the lock for the casement window? Happy to send a picture as needed.