Rounded bolt, need help

I’m in need of ideas on how to get rounded Allen key bolt off, I’ve tried sizing up(just rounded more) tired vice grip(the way the bolt is it just slips off because of the way it’s tapered) I’ve tried drilling it out and using a bolt extractor but it just snapped off. Is the only option I have welding a socket or a Allen key onto the bolt and getting it out? Open to any suggestions. It’s on a 2005 gsxr 750 it’s the bolt for the brake caliper