Most all my recent purchases of audio books are digitally purchased and downloaded. Our public library also has an extensive collection of digital downloads, and they tie into many other library systems that makes for a huge selection of books available. The library still has tape and CD copies on the shelf too, but I've gone through a lot of the available titles.
I belong to
Audible, part of Amazon, the monthly fee earns me credits that can give pretty good discounts on audible books.
Have you tried
Librivox, free audio books? I've found good and poor volunteer recordings of mostly public domain books, but the price is right.
OpenCulture has 700 free audio books.
Many other resources available through a Google search.