Have you tried standard jewellers screwdrivers? I've found the the flat tipped ones that are slightly oversized for the diagonal head rebate can be wedged in... diagonally... and can give you enough grip to start the screw moving.
I tried it and even though it was tricky with the screw being in a small recess hole (Top front right shell cover) I managed to get a small rubber band in but it would not bite/grip : (
I am not giving up "Screw that screw!" I will find a way...