I purchase my audiobooks from libro.fm. It’s like Audible where you subscribe and get a credit every month, but part of the profit goes to support local book stores, and the books are DRM free.
Probably worth noting as an aside that bookshop.org is sometimes mentioned as a libro.fm-like Amazon alternative for ebooks (NOT audiobooks), but my brief experiment with them was awful: they were much, much more restrictive than even Amazon, at least before Amazon's removal of file download.