I bought mine through eBay, but I see they have their own site as well.
http://wings-suspension.com/manitou.html
This brought my Manitou 4 back to full function. It is important to note that Manitou forks had no damping function (other than the stiction of the fork legs) until the EFC, which was the final evolution of the first generation (Manitou 1-4) after which came the redesigned Mach 5.