Main feathers on the ENDS of the wing, alot of times these feathers are damaged do to " strutting" or " draging" their wings during the breeding season.

You can save some money by doing it yourself, just lay the feather down on a cutting surface, so the feather " bows" , or " arches" up, then take a sharp knife and cut down the center of the " spine" of the feather, ,Now you have 2 feathers. Trim to length and your done. Modern glues work fine. You can die color them also>

Try it, its fun to do it yourself and cheaper, good luck.