You may want to contact KBelov at benzworld.

http://www.benzworld.org/forums/w124-e-ce-d-td-class/1443986-cabriolet-fluid-leak.html

Otherwise, there is a source (Dennis Ficken) who can repair your cylinders for $35 each cylinder plus shipping. He repaired all of my cylinders. The link above contains other links that should get you what you need to know. There's no need to go to the dealer for parts.

I believe the W129 models have 12 cylinders. It is best to have them ALL rebuilt at the same time.