Get a Torx socket that is just slightly larger than the hex opening and tap it into the hex opening with a hammer. The Torx splines will bite into the metal and you should be able to remove the bolt.
*Note: I would remove the shift arm and lay it on a solid surface to tap the Torx bit into it.
Ed
*Note: I would remove the shift arm and lay it on a solid surface to tap the Torx bit into it.
Ed