Worn out (stripped) screws in Macbook Pro - how to remove?
I would use locking pliers to take it off, then take the screw to a local fastenings store who should be able to sell you a similarly sized screw with exactly the same thread.

You may want to add Loctite, Apple usually uses Blue 242 Loctite on their screws. You can get cheaper brands, but make sure it's coloured blue — that's the strength of the glue.