Sally
We don't have them either. But basically any "plain" sweet biscuit (biscuit as the British Commonwealth would know it - LOL) will do.
I often use a crumb base for my unbaked cheesecakes and pies but I usually make it up on the day. Biscuits and butter is the basic mix. But I normally cut down on the butter and add some copha to get a nice hard set shell. This is easier to cut in slices without crumbling, and it holds firm outside the fridge better. It also cuts down on the rich buttery taste. I add nuts, cinnamon, nutmeg, icing sugar and/or coconut - depending on the filling. And for my fabulous creme de menthe pie I add cocoa and coconut for a beautiful dark choc base with the lovely light green creamy filling.
There is nothing politically or medically correct about my desert cooking!!!