Well, if you're looking for spy novel audiobooks, consider checking out Librivox. It offers free public domain audiobooks, and there are quite a few classic spy novels in there. Also, some independent publishers have their own websites where they sell audiobook versions of their spy novels. You can search for these publishers by looking at the back of your favorite spy novels to see who published them and then visit their sites.
There are several places to find spy novel audiobooks. Amazon is a great start. Not only can you buy physical copies of spy novels there, but also their Audible service provides a large number of audiobook versions. Additionally, Google Play Books also has a selection of spy novel audiobooks that you can purchase and listen to on your device.
You can try Audible. It has a vast collection of audiobooks, including many spy novels. Another option is your local library. Many libraries offer audiobook lending services either through their own apps or platforms like OverDrive.