Those metal substrate converters that EV0SP0RT sells are EXACTLY the type that I'd recommend. I'd price them at RandomTechnology dot com, and call around to the local muffler shops. If everyone appears to be shafting you, and you don't mind the drive, call Rick at R G Brakes Alignment & Mufflers (661) 259-7098 - 24309 Creekside Road in Santa Clarita. Rick does VERY GOOD work. He's helped me out with photos for magazine articles and worked on my personal cars. If he doesn't have metal substrate converters, he can order them.
If you go to Ricks, let me know. I'd like to take some photos while he works on your CLK for a converter article. In fact, wherever you go, please shoot me a note. I need the photos. Thanks