you need 6 of them, right? I believe that one of the spacers is built into the cogs, the one between the 12T and 13T (or 13, 14, depending on which cass. you are talking about)
I might have some, can't remember how many spare I have though.
EDIT: Seems I have some 7 speed spacers on double checking as they are 3.16mm...good luck hunting