Bring a small vape pen or disposable you wouldn't mind losing as well as a couple of small bottles of
juice.
If you've been to China you'll know you'll be able to find whatever you want over there pretty cheap just don't take anything you'll regret losing. While people have been able to bring in mods and
juice you'll find cases of people being stopped just eliminate the problem before it happens.
Take one 10ml bottle with a small cheap mod or better yet a couple of disposible pens and check your larger juice bottles in sealed plastic waterproof sandwich bags with your luggage.
If you're sight-seeing you'll find ALOT of shops and other tourist areas where you'll be able to buy some stuff and bringing that back to the US should be easy peasy as long as you remember to check the juice.