Plastic window part

Hi There,

I have Viking plastic double paned windows That have an extra locking mechanism down low that is a bolt that screws into a post within the window itself that can be pushed down into the base of the sliding portion of the window frame an inch or so from fully closed. This allows the window to be locked in a slightly open position for air flow from outside.
I am missing the bolt that screws into the post that can be slid up or down to lock in an open position.
The bolt has crosshatches on the outside edge of the flat head with a short screw stem. It looks like some sort of brass to me. I can send a photo of the bolts I still have in other windows.

Warmly,

Heather