Hopefully, you still have the bottom half of the hinge that was attached to the window.
As far as I know, individual parts are not available.
You can go to a glass company and have them cut a new piece. Use the other window and trace it to make a template. If you have a piece of glass made, bring it to an auto glass company and have them glue the hinge on. they use a primer on the glass and a windshield adhesive. I had mine done this way. You can also consider Lexan instead of glass.
Do a search on this board about replacing the rear window glass. Lots of good posts and suggestions.