About a year ago I needed a replacement battery, and did talk to Tom at Classic Center, he told me same story that the battery for our W113s was discontinued. So at that point I started calling a round to MB dealers up and down the east coast to see if they might have a leftover MB white battery NOS (A 002 541 87 01 26), and low and behold I found one. So you might try checking with MB dealers.
Bob