I saw a complete manual sunroof just last week on eBay.

Ah here it is... not sure its the same as for the 240D but... I think it is

I don't know the seller and so your on your own...

http://cgi.ebay.com/ebaymotors/Mercedes-w114-w115-w123-Manual-sun-roof-assembly-300D_W0QQcmdZViewItemQQ_trksidZp1638Q2em118Q2el1247QQcategoryZ140719QQihZ005QQitemZ150189668740QQrdZ 1QQsspagenameZWD1V