I'm surprised you're finding it so difficult to local gluten flour/wheat gluten. It's not like it's just some exotic vegan fake meat ingredient; gluten flour is an ingredient in most rye breads, so any place with a large baking section should have it. I used to find it in bulk bins in health food stores and pre-packaged in grocery stores, but lately I've only found it pre-packaged in both. It's usually
this brand, but there are other brands as well. If you live near any of
these places, you should be able to find
it.