Assi brand Gochugaru is labeled as gluten free. Hasn't seemed to set off celiacs in the family, but don't know a lot about the company. We get it at our local Asian market.

Here's what one looks like on amazon (I know they have different spiciness levels)

https://www.amazon.com/Hot-Pepper-Powder-16oz-Coarse/dp/B00RH8E72A