My way of doing it will probably be really long winded and there will be a better way of doing I'm sure someone will come up with on here , I would get some 1mm thick angle steel , hold it so the thin edge would take the rubber to hold the sceen , make some marks where the curves need to be and cut some slits in it to bend to form curve of screen weld in tacks straight away or it will distort , repeat that the whole way around and You will have a ugly surround that will hold the screen and its rubber , that's the hardest bit the rest after you've sat it on the car , its fixings and cutting the lip off to weld a steel tube on it , I would use the old one as reference of measurements to make it look the same