This is simple.
Do you have a Whole Foods nearby? Simply purchase their organic non-GMO verified yellow corn tortillas. They are 12/$1.49. They're in the photo below:
If you want the long explanation, you want the tortillas to have three ingredients: Corn, water, lime. Or it could say "treated with lime." It's important to note that this is NOT lime juice - it is calcium carbonate - bagged lime from the hardware store. It kills the mycotoxin inherent to corn and eliminates the phytate/increases B vitamin absorption. It turns a mildly irritating grain into a pretty clean starch that's correlated with healthy societies, similar to how white rice is correlated.
The other thing I recommend: purchase organic corn tortillas, or at least tortillas that are non-GMO. Trader Joe's is viable option. They are not organic like the Whole Foods variety, but TJ's doesn't carry GMO's. The Whole Foods variety is far tastier, though. The TJ's ones are comparatively flavorless since they're made from white corn. I really don't like the idea of GMO corn. The non-GMO organic stuff, I have less qualms with.
Don't put your trust in anyone on this forum, including me. You are the key to your own success.