Hi Hcal....
I've dabbled a little with crusts...
I am assuming that a chocolate wafer cookie is a chocolate graham cracker...yes/no?? If it isn't then they sell chocolate graham crackers at most stores that should make a nice substitute here.
If your local store doesn't carry chocolate graham crackers then maybe you can pick up some regular graham crackers and make your own chocolate graham crust using regular graham crackers, cocoa, sugar and butter...see the following recipe link..
Howstuffworks "Chocolate Crumb Crust"
MARK