Fork Disassembly Tool

The bolt at the bottom of the fork can usually be removed with a quick snap of the wrench if the fork is fully assembled.  A little compression can help. 
An impact gun will usually work if you have one.  Don't lose the fiber washer.

If you must have the special tool to hold from the inside, this is an option:

Joe McDonald wrote: The 3/8 Gator Socket just arrived from ebay, $12.88 - free shipping. Nice snug fit down the H2 inner fork tube to hold the cylinder fork and good for other stuff you least expect. Fits 7-19mm.

 

Another Option

14mm socket slightly squashed

modified lead pipe

 

And Another Option

Darth wrote: All I did was take a long 3/8 bolt (Grade 8 bolt) and ground it on the bench grinder to the above dimensions. Then used a hack saw to make the slot for the roll pin. They say to use special tool XXXX. I just used this (with about 2 miles of 3/8 drive extensions) to hold the cartridge while I tightened the bolt.