Had a similar problem several years ago with my outdrive. I got several quotes, all well over $200. All the marinas that I talked to sent them to a welding shop (never found out where) for winter work.
I saw an ad for Skeggard (
www.skeggard.com) and decided to give it a try. It's made from Stainless, custom made for the skeg that it fits over. As I recall, it was about $99. It required drillling two holes in the existing skeg and is attached with both bolts and epoxy. It was real easy to install and worked terrific. I'd highly recommend it.