These covers carried over a bit into the 107 cars, I found one, with the metal snaps as Joe writes, on ebay a while back. The part number I have on the original one from my 280 SL is 000 158 06 85, and the number is on the side of the unit. There is also a Bosch part number -
1 235 510 000
As an FYI - I bought mine in October 2013 - $110