I do not know who sells the specal tool. According to one tech in the following thread, it's around $100.00.

Look at what Jim Kimmey had to say in this same thread. His approach may work for you.

Locking Crankshaft Pulley Securely

__________________
Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"