I've been looking for this part for WEEKS as well...this is the first site I've seen that even lists it...and it's out of stock. FML.
I spent an hour at my local MB dealer trying to convince their idiot parts manager that there is, in fact, a spring under that plate that needs to be replaced. He called MBUSA corporate, and came up with nothing...and gave me the standard "there are no owner serviceable parts...blah blah blah."dealer usually stocks the spring, or can order it for you. Its actually cheaper from the dealer