A few years ago on a week-long bike tour one of the participants bent his der hanger on the first day. Local bike shops are unlikely to have one that fits your bike - its usually a special order part. Anyway, the bike shop in the local town did not have the part & could not bend it back, so Jim ended up buying a new Trek Madone right then & there. As you can imagine, he instantly became a legend on the ride. Now whenever I do a bike tour I make sure to pack a derailleur hanger. I dont want to come home having to explain a new bike to my wife.
Good advise. I started carrying a spare about 3 years ago after a mild crash bent mine. It was a really close call as we bent the hanger back into shape. Was 10 miles from nowhere.