It got 6 upvotes, and two answers so far.
But how can anyone really know the OP's limitations? 'Easy to find in the US' is not an objective measurement. DC, LA, and NYC all have Chinatowns with different bookstores. And the selection in each bookstore is not going to be predicated on anything objective!
It's anyone's guess what random selection of books the OP has access to, and that means the question is inherently vague and subjective.
One answer begins:
I take the opposite view.
OK, if you can 'take the opposite view', in my opinion it's not fit for StackExchange, it's fit for a forum.
I see a lot wrong with this question, though. Not just that.
I find this question interesting, but too localized to be useful to anyone but the OP. The world is a shrinking place, and if you're intelligent you can find any book for sale online. It's much different and much more difficult importing stuff from China in Europe. (People in the US have it so easy that frankly, it's a bit strange to me that anyone would insist on not doing so.)
So I have a very hard time imagining what kind of google search would lead someone to this question. I think it's vague, localized, and subjective. Because of the way it's been asked, it's not even about Chinese.
Also, US-centric questions should not be asked here, in my opinion, unless they are about US-centric properties of Chinese, i.e. as it is spoken in Chinatowns in the US.
What do others think?