I recently pulled my fender liners, arches and fenders off of my 1999 G500. I was dismayed by the condition of some of the brackets holding the plastic pieces in place. They had all rusted and some of them were getting a little thin. I remembered Hans Hehl had done a write up on fabricating stainless replacement brackets and decided that I would do the same.
http://www.hehlhans.de/engtipp1.htm
I ordered a couple of new brackets from Mercedes. They are normally $20 each retail, and 16 are required per vehicle. Not wanting to fork over $320 for a new set, I pounded one of them flat and ended up spending quite a bit of time working on a sheet of stainless before finally throwing in the towel. There is a sheet metal and fabrication shop down the street from where I work, so I brought in new dealer supplied flat and formed samples to get an estimate for making a handful of them. They used a CAD program and laser cut them, doing a nice job of duplicating the flattened bracket and with a couple of whacks with a hammer in a vise and I had new stainless brackets on the G. I ended up having a hundred of them cut and will be selling off the extras to cover my costs.
Cheers