Before you do that get hold of a mates 2mm driver it may still be able to be unscrewed with a decent driver, don't use to much forcethough i tend to use a hudy driver with a plastic handle and put a another allen driver ( strong one another associated or hudy ) and using the the leverage effect to gently loosen the stripped screw from the chassis, try this first before using more damaging methods.

You can do this with a quality t-bar driver but finding a quality one is as rare as hen teeth around these parts