If it's the protruding brake spring tension screw that has very low torque and is easily turned, then a simple pair of pliers would work.

Otherwise you could use pliers that are designed for removing stripped screws like the pz57
http://engineertool.wixsite.com/engi...l/screwremoval

If it's a recessed bolt then you could use the dbz extractor.

But as other people have said, a sacrificial torx or other key is the cheapest method.