Russian parts website appears to be down
 

Any other options, reasonably inexpensive, to identify part numbers?

Sign up for a membership at epc.net online MB's official electronic parts catalog. It's free but you have to be in the US (I think Houston still is), provide a valid credit card number which they will verify by issuing a $1 charge and then rescinding it the next day. Also you need to be using Windows and have Java installed. Subscription is for 1 year but not sure if it's renewable.

Answer
 

Mercedes Service Manual thread, CD/DVD/Paper
http://www.peachparts.com/shopforum/general-information/248948-mercedes-service-manual-source-cd-dvd-paper.html