I hope this suggestion helps, but go for bread. I'm pretty sure supermarkets should have gluten free bread options. My nutritionist also told me that if you toast it your stomach won't get bloated as much and you'll be able to eat more shortly after.

If that's no good for you you could also try gluten free cookies/pasta. I buy those cookies all the time and they're good snacks. Some varieties of tofu also have more calories than regular cheese.
best of luck!