Mate,
There's no way to fix your cracked screen - the only way is to either make a new one, or write the manufacturer and order up a new one.
There's no way to repair the crack and make it invisible - whatever you do to it, you'll still be able to see the crack. The easiest thing to do would be to dip the cracked back screen in Future, allowing Future to seep into the crack - when it dries, the intensity of the light refracting off of the cracked edges will certainly be less, but you'll always be able to see it - and this repair would do far less damage than trying to slip some liquid glue into the crack.
Good luck, mate.