What sort of audiobooks have you tried?
I have to have a semi-interesting, semi-dull non fiction book, read in a soothing voice, if possible by a British author. Nothing emotive but interesting enough that it distracts my mind from whatever I'd like to be thinking about. It needs to be fairly quiet so it sounds quite distant because that makes it more like I'm already falling asleep.
If it's really bad I sometimes put the sound of a stream over the top of it!
The other option (again sometimes layered on top) is thought exercises to distract me. So naming 4 objects beginning with each letter of the alphabet, or as many as I can for each letter. And I build a scene with all the objects as I go, one scene per letter like a children's alphabet book. One could probably do a scene with all the letters if you were going 4 per letter.
You can also do the same thing with categories - as many butterflies or trees or cars that you can name.
Or planning out the house I would have if I won the lottery (a highly academic exercise as I don't enter the lottery).
The aim, for me, with all of these things is to create a slightly dreamlike quality, so abstractness and maybe things that don't quite fit together is all okay, even beneficial.
Or counting backwards in 7s or 3s or whatever is difficult enough to occupy enough of your mind for the rest of it to go to sleep.
Paul McKenna has a sleep hypnosis thing on YouTube which is quite effective but annoys me because my phone screen stays on. I suspect if you find it works (for me it does but not often enough to bother) then you could find a paid for version that didn't do that.