HydroBoost Part Question

[KYBlueOval]

I've mounted a 2003 Mustang HydroBoost unit to the firewall of my Ranchero,and would like to replace the "Rubber Boot" that goes through the firewall covering the operating rod. The Ford part number is   XR3Z2B022AA  but Ford says it is No Longer Available.
I've searched many sites on line, but to no avail. Any thoughts on where I can obtain one?
Thanks in advance,
John