If you're lucky, you might find some torrefied ("puffed" or "popped") gluten-free grains at a health-food store. I brewed a quinoa IPA with a mix of sprouted quinoa, roasted quinoa, torrefied quinoa, and "rice crystal malt cookies" that I made by grinding up some flaked rice, mixing it with amylase and water, and then baking it at low temperature for several hours. That IPA had the most insane head retention of any beer I've ever brewed...it would hold half a finger of head all the way to the bottom of the glass.
Generally, though, maltodextrin gets the job done nicely. Especially in a partial-mash or all-grain brew.