You get a rock up in there? If the only real damage is the one missing tab, I'd throw some new pads in and run it. Just make sure the pads don't have enough movement to reach the bobbins. Other option is to buy one used, pretty much all SM Husky calipers are interchangeable if they're the same type (axial vs radial mount)
That's the side of the caliper between the spokes and the rotor and it's the upper part. How could something have hit that point? And how could it have broken without any bump? That's odd! Did you unintentionally drop the caliper after having removed it? Maybe you could make someone weld the tab (edit: or a piece of aluminium) and the caliper with a TIG welding.
If a chunk of gravel got thrown up and wedged between a bobbin and the caliper tab or bake pad, it could do that kind of damage. Check both ends of all of your bobbins to make sure none are damaged.
