Well I "only" had to look at 13 pp of "misc", after looking in other catagories before i found one- in the past there have been others, but i think i have redeemed myself with 13pp etc. I hope
http://www.surplusshed.com/pages/item/m2816.html
i wonder if a search with "ground glass" and no plastic works
Search engines are inscrutable, and annoying- bastids as it were
Good Luck
regards
Ed