@liuzhou, just out of perverse curiosity I search Amazon and there are indeed several "Chinese Mustards" or "Oriental Mustards" for sale. The comments are hilarious. Most people don't like these products because they don't taste like "real Chinese Mustard!"
Here is just one example: https://www.amazon.com/Ty-Ling-Mustard-Chinese-Hot/dp/B008VSYACW/ref=sr_1_13?