I couldn't get bleach to work on my old Duo R controller either. It helped, but it made it a yellow instead of brown, that thing was nasty. I was wondering about the white PCE CD drives, it sucks that bleach won't work on those.
Similar to Keith's sanding pad, I've had good luck with Mr. Clean Magic Erasers on the Duo R. I've tried it on two different Duo R's and they both look brand new again, but they weren't really yellow, just covered in black marks. Be careful around the logo though, a Magic Eraser will remove it!