What's an online store that doesn't allow chinese knock off today? Amazon used to be good, a stamp of "This is quality" but now it's a numbers game and the quality is a dice roll.
Amazon is still fine if you're looking for a name-brand item, but as soon as you leave that path, who knows what you'll get? Don't take my word for it, but I even remember reading about their "Fulfilled by Amazon" program substituting items from different sellers with the same SKU. The result was predictable: people scammed the system by mis-labeling cheap knockoffs.
Now that Amazon makes so much money off AWS, maybe they could use a bit of it to put third party sellers in their own "Wild West" tab, and taking a bit of responsibility for what they sell.