<<Disclaimer: Verify this information before applying it to your situation.>>

From the UK Coeliac Society food list valid through April 1988:
Gluten Free communion wafers are available from:
The Poor Clares
Monastery of St. Joseph
Lawrence Street
York, YO1 3EB
England
They ask that members give in full their name and address and the name and
address of the Church usually attended along with a donation to cover the
cost of the wafers and postage.  (Keep in mind that this is for the UK...so
if you are in America you may have to write to them to find out if they will
supply out of the UK).
Jane Oswaks, London