Bought my new battery from the local M-B Dealer about 5 months ago.
$ 120.00.
Just do a little negotiating ( whining ) with the parts guy.
On another note, when I visited the " Interstate Battery " display at last years SEMA show, there was an M-B battery ( complete with the M-B Star ) on display.
I questioned the fellow about it, and he explained, yes , they DO make batterys for M-B.