Are you going to oversize the next bolt or make new threads using some compound? At this point I'm assuming new thread.
New threads via inserts. Going over-size isn't practical, and probably impossible in this case as the damaged mounting boss is for one of the caliper guide pins.
Don't buy any tools. I have them.
Too late, I already have a heli-coil kit in the appropriate size (M10x1.25).
Pricey kit, but nowhere near as pricey as a replacement caliper.