Thanks for responding. I guess the big problem right now is that I
don't even have a recipe to use as a starting point. The ones I've
found thus far call for ludicrous combinations of ingredients --
multiple grains, multiple binding agents, and so on.

Does anyone have a good recipe I could try to modify?

Gum is a deadly allergen, no different than peanuts, but there isn't
much information out there about it, which is probably why nobody has
written any cookboks that offer gum-free recipes.

Thanks again for the replies.