I was able to find a new left-hand lower fender extension for my Spyder restoration but not a right-hand one. In looking at it, it didn't seem like there were that many difficult bends in it so I thought I'd have a go at making one from scratch.
So I made a buck out of some red oak from a shipping pallet. I made it as a mirror image of the right-hand one.
Then I bought one of these really cheap sheet-metal brakes from a tool store we have over here called Harbor Freight. They don't sell what you would call professional grade tools but a lot of the stuff they have is very worthwhile.
After that, it was just putting the folds in and then beating the edge around the wooden buck. To do that, clamp the metal to the wood where you can and work it with a hammer around the edge.
Sanded it down with a DA sander once I beat down all the high spots
Holes added at the end.
After patching-up the bottom of the fender, I welded it on.