How do counter hold the water pump to remove fan 602

[biopete]

I'm trying to remove the viscous fan clutch on a 602 2.5 T in a W124 to change out the vac pump. I can't even get the plastic fan shroud out without removing the fan .

I have my 8 MM allen on the bolt but i just cant hold that pulley still. I had someone push on top of belt while i turn but it keeps moving. The manual says use counter hold tool which looks like just something you put on and push down?

What do you all use to hold the pulley or how do you do this job? Does sears have a pulley holder tool?

Thanks