the black casement track slider broke off

Thanks for reaching out! I believe the piece you are referring to is the track slider typically connected to the casement window hinge. Unfortunately, this is not a piece we sell separately from the hinge and I am not confident that any other companies do either.

That said, you'll likely need to replace the entire window hinge. I am happy to recommend a replacement but I'll first need to confirm the length of the track installed to the window sill.

In the meantime, take a look at the tutorial below for an idea on how to remove and install your window hinges.