If the piece that broke is part of the little lever thingy that you push to release the wind screen from the roll bar then it is replaceable. I replaced both a broken clip on the roll bar and the lever part on the windscreen itself. The part that attaches to the roll bar is pop riveted; the lever piece on the wind screen just pulls off and the new lever pushes back on.
Like I said above in bold type, this is not the little lever that pops off and can be replaced. Nor is it any part of the pop-riveted pieces on the roll bar itself.
This is a little pin on the black plastic surround on the windscreen itself.