Thanks for the replies ... it seems to be a difficult size to find. Now I see why they asked about the material so they could make the washers themselves!
if you have the specs on the material you can usually get sheets of material from mcmaster carr and then die cut it
we have done that before also
so of these military jobs require gaskets, washers, filters and other things
made from blotting paper, nylon, brass, stainless, all kinds of weird stuff you can't commonly find and they usually have it...good luck