I don't think such as thing exists sadly. I had high hopes fir UE fits, but while the fit is great, they stick out too much for side sleeping.
They also had an annoying firmware issue where tapping didn't work until they quietly rolled out a fix and I happened to see it months later when I googled the issue again.
We're not in the sleep earbuds space, but at https://soundmind.co we're making an eeg headband with bone conduction sound to improve sleep performance via auditory stimulation.
Auditory stim doesn't help you fall asleep, so we let you listen to whatever you want as you fall asleep, when we detect you've fallen asleep, we stop whatever you were listening to, and switch on our stim.
I don't really care about stim, but pausing my book after I fall asleep is HUGE. Right now i use a sleep timer which is okay, but if the book is good and stops before I fall asleep, I need to really wake up and set a new timer. If I set a longer timer, there is a chance I will fall asleep early and have a hard time finding my spot later