Would you by chance carry the part in the picture. It was in the casement track. The crank arm has a small ball which clicks into the top of this nylon and its what controls the window moment. thanks Marty
Casey from SWISCO responded:
December 11, 2018
Hi, thanks for reaching out. The part from your photo is only sold with the full operator track, 39-543 if you would like to give it a look.