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

A handy person from Bemidji, MN says:
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,
Profile picture of Tom
Tom from SWISCO responded:

Take a look at our 91-179 . Could this be what you're looking for? It's tough to say from your picture, but the knob at least appears similar. 

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