If you are talking about the mounting flange with 4 holes in it, if it's not available as a patch panel, then you either buy a crashed fender with a good flange or you make it. Not that hard to make. If you don't have shrinking/stretching/flanging tools, make it from two or three pieces. With a hammer and some "mandrels". Then weld it on the fender. Use the old rusted piece as a template.

Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn