What about abebooks?
* Alibris (aggregator like AbeBooks)
* Better World Books (B Corp)
* ThriftBooks
* Bookshop.org (benefits local bookstores)
You can also connect directly to nearby independent booksellers on https://www.indiebound.org/
I think it's run out of Charlotte.
AbeBooks had told bookshops in countries including Hungary, the Czech Republic, South Korea and Russia that it would no longer support them from 30 November, citing migration to a new payment service provider as the reason for the withdrawal. The move prompted almost 600 booksellers in 27 countries to pull more than 3.5m titles from Abebooks’ site, putting them on “vacation” as they cited the motto of the International League of Antiquarian Booksellers, “Amor librorum nos unit” (love of books unites us).
https://www.theguardian.com/books/2018/nov/08/amazon-abebook...
<drops into depression>
Overall the US seems to be incredibly open to monopsonies, monopolies, and oligopolies, and very hostile to any restraint on such things. Though, the merest hint of success from a non-US entity seems to invoke bipartisan terror and pleadings for sanctions and new regulations. Funny that.