MB will give you free for a year the Electronic Parts Catalog
(They will use a US based credit card number to verify residency) :
https://epc.startekinfo.com/epc/subscribe.jsp
Or if you've no access to credit card the Russian site:
http://www.detali.ru/cat/oem_mb0.asp?TP=1
(Much more user friendly,in my book)
EDIT: Yeah,I thought I dis-remembered posting those pesky seal ring part numbers...Reply #4 In This Very Same Post.
"...Teach a Man to Fish..."
I'm outta here.