I think the closest "natural" mouthwash you are going to find is going to be Tom's of Maine mouthwash. I already checked it out and it doesn't include the key ingredient of Cetylpyridinium Chloride that assisted with Sargvy's recovery from EC.
But, by all means, still try to find something else. It surely never hurts to scout around.
But honestly? If you want my opinion, the only way you are going to really know if a mouthwash is 100% natural is if you make it yourself. You can incorporate an oil pulling oil as your foundation then add things like baking soda, peppermint oil & other beneficial ingredients. The thing about commercial mouthwashes is that they add chemicals that preserve the other compounds so that the mouthwash won't go rancid at room temperature or if it is stored for a prolonged period of time.