Welcome to the JG!! You're talkin about the Miller Special Tool 8512A which has been superseded by the SPX Miller Special Tools Damper Installer. You should be able to find it here at millerspecialtools.spx.com. If you're in the states, you should be able to rent one from either Advanced Auto or Auto Zone.
2001 Silverstone Metallic WJ Limited
2005 Black Chevy Tahoe Z71 4x4