Stop knob to lock and unlock glass plane in storm window so it can be raised and lowered

I need 4 of these thumbscrew stops that you slide right to uncatch the window slide so the window panel can be raised or lowered to a new stop. I assume they unscrew and screw in. I can't find them anywhere. Do not know brand of window.

Thank you,

Hello, I was wondering if the poster ever solved the problem or found a solution? I am looking for the exact same thing! Thanks.