When you buy a Kindle book, you're usually offered a discounted price if you want to buy the Audible book as well. Now, if you don't take it up at the time you can still get the discount but it's a bit more of a faff.
You need to be logged into your account and go to https://amazon.co.uk/matchmaker (or whatever your local Amazon site is) and it cross references the books. I can't see a way to search, but you can just browse through.
As my commute is longer these days, I'm tending to listen to more podcasts and audiobooks, so this is an interesting option to take up.
22 January 2020