Found this website supplier (China) of Disc Brake Splash Guards (Backing Plates) for a wide number of applications. Using the M-B P/N's per the attached file, the ones for the Crossfire NA & SRT-6 can be found. CLICK

Later,

 

That is good info, as long as they are not made of aluminum. I had trouble with them on my 2007 Chrysler 300, they were originally made of aluminum and were attached with steel screws. The winter salt ate them at the screws and left small bits of aluminum under screw head that looked like washers. They both went and were replaced, made a heck of a noise rubbing and bouncing against the rotor. The new ones were made of steel, I guess someone learned a lesson about galvanic corrosion.
That 300 was the worst car I ever had, I swore that I would never buy another Chrysler.

 

Looking at the capabilities of their manufacturing, these may be a plastic compound. Looks like they have quite a few injection molding machines. Wonder how a plastic would hold up long-term?

 

The part I looked at looks like plastic because of the thickness of the part. It would take a lot of tonnage to make a part that thick in steel even aluminum.

 

Just to confirm, I asked OE Discount Parts if the SLK splash guards are the ones that fit the corresponding Crossfire model. Received confirmation today (see attached).