Mine just broke - right side. Looked for replacement part but pick'ns were slim and prices outrageous. Read about the fix with the printed part but wasn't sure about the color matching. So I fixed it with duct tape and wheel tape weights:
1. Align the flap and base hinge points with each other. If the hinge pin is available, use it to aid in the alignment of the flap.
2. Take a strip of duct tape of appropriate length and stick it to the underside of the flap and base with the flap in the up position while maintaining its correctly aligned position. I used black duct tape to minimize attention to it.
3. Check if the flap remained in the proper aligned position by moving it to the closed position. It should rest on the adjacent edge that holds it even with the top cover. If it is not ok, reinstall a new piece of duct tape with the proper alignment - in other words, start over.
4. If alignment and movement are ok, glue one or two wheel tape weights to the underside of the flap. I found some weights already painted black so didn't need to paint them. Do not rely on the tape weight adhesive strip to hold the weight in place - it is not meant to hang upside down for long. Use construction glue. Use masking tape to hold the glued weight in place until set. Be sure to locate the weight(s) in a location that does not interfere with the top's hinge mechanism. I used one 3/4 oz. weight in the rear-most and highest position with the flap in the open position. I found that this position avoids any conflict with the top's hinge mechanism.
Hope this helps.