Since the early 90's replaceable derailleur hanger have been common. I am amazed at how often I ride with someone who doesn't carry a replacement. On a recent ride 2 riders caught sticks snapping the hanger in one case bending the other. Had the hangers not been sacrificial not only likely a broken $300.00 rear derailleur but a long walk in mountain bike shoes would have resulted. And really mountain bike shoes are comfortable while clipped in but walking miles in them is no picnic.
We have most common hangers in stock made by Wheels Manufacturing.