Good quality duct tape works good. The shoe goo and drywall mesh works good too. Gorilla tape is awesome. Thought I might add; It's a good idea to drill or punch a small hole at the end of the cracks in the lexan. That will help to stop those cracks from growing.

Personally, I wouldn't bother with any kind of metal roll cage. I've seen lots of people buy them, use them for a short while, and remove them and never use them again.