I tried a couple of times to find certain audiobooks, but seldomly had luck. There just does not seem to be a place that sells digital versions of audiobooks, similar to how bandcamp sells music.
And even putting on my eye patch and throwing out my fishing net I was not able to find a place to get them.
I do not want to use a subscription service, especially if it’s part of amazon.
Therefore it seems buying a CD and ripping it is the only option left.
In addition to all the suggestions everyone has put in, check your local bookstores. My local Barnes and Nobles regularly stocks audiobooks (or did, I’m not allowed in book or tech stores without “adult” supervision anymore :), both in audio cd as well as mp3-cd. If they don’t have what I’m looking for, often they can special order it. Just have to ask.
For me though, Audible is cheaper. I’ll buy the books, download them and strip the drm off.