That's a good one, Is the part broken into two pieces? or just a cracked windshield? With cracked plexi windshields it's common to try to drill a hole at the end of the crack to halt its progress, I've done this years ago and it worked alright. But as to using some sort of glue to hold the pieces together....I've neve heard of that or tried it myself, maybe you could drill a few holes and sandwich some lexan around it with some clear silicone, and bolt it on tightly? Replacement windshields are available if it comes to that, or take your beat up one to a glass shop and have them trace it onto some Lexan and cut you out a new, really tough version.