On my 94 Marathon I have the pleated shade set up. Not only has the strings broke but the retractable mechanism broke also. Marathon told me to send them back also to "see what they could do". I would rather buy new ones but have had no success with who produces them.
This is as close as I could find!! http://www.dashguard.com/
Hope the link works.
My last call to Marathon I was told the bus is so old they may not have parts any more. I refuse to call them again...this month!
I was happy with the way they work and want them back.