<<Disclaimer: Verify this information before applying it to your situation.>>
In Germany, the gluten-free community has a wafer called backoblaten, that I
believe is for a cookie backing. This is made of corn starch, water and raoe
seed (canola) oil and looks just like a communion wafer. With such a
simple composition, it micht be easy to make it into a recipe for communion
wafers.
Martha Teeter