A worn out file cut short and ground to a fine straight edge makes a great scraper better than you can buy. Also if you have extra allen wrenches they make great easy outs. Choose a allen wrench just smaller than the offending bolt center drill a hole the same size of the flats drive the allen in the hole a little twist and out it will come. I've used this method on many wheel cylinders to remove broken bleeders with out failure. I think the heat from drilling and the shock form driving it in helps loosen the broken bolt.
