What are the options when looking for gluten free chapati?
I use ivory teff tortillas from La Tortilla Factory as a gluten-free substitute for chapati. They are sometimes available at my local grocery store, but I've also bought them online. They are similar in texture and mouthfeel to wheat chapatis. When heated on a griddle, they brown and puff up just like the real stuff, and they then taste delicious with a little ghee. I don't miss wheat chapatis at all since I discovered these. They are much closer to wheat chapatis than gluten-free sandwich bread is to the genuine article. They freeze well and also keep in the refrigerator for several weeks. 

If you're interested in making a gluten free Indian roti, I would suggest not trying to make something that approximates chapati. Instead, make some traditional preparation that uses other flours. For example, there's bhakri, which can be made with any of various flours like jowar (sorghum), bajri (finger millet), or even rice flour. 

Or there's one of my all time personal favorite foods, a multigrain flatbread called thalipeeth. Most recipes online include wheat as one of the ingredients, but you can just leave it out and increase the amount of the other flours proportionately. There's also a sabudana (sago) version which is a lot simpler as it just uses whatever flour you have lying around in addition to sago. 

Finally, the site Spice Up The Curry has a section on Indian Breads that includes recipes for rotis made with exotic flours such as rajgira (amaranth), singhara (water chestnut), and kuttu (buckwheat). I've never made any of those, so YMMV. In general I've had good success with recipes from that site, though.