If you baulk at the idea of driling the caliper, then remove the caliper, saw through the retaining pin, undo the bolts holding the halves together, split the caliper and remove the pads and hardware. Grip the sawn end of the pin hard in a vice and gradually twist, wiggle and pull it loose. Clean up the hole with the right size drill and you can then reassemble with new pin and copperslip. In theory you should change the seals while you're in there but with care, cleaning and a thin smear of RTV between the halves you should be OK.
