I use one of these. They have more expensive ones that have a post that bolt underneath the seat rail but you have to be turned a little and wasn't comfortable for me after a while.
I paid good money for this and I’m damn well going to use it as often as I can.
https://www.amazon.com/XERGUR-Steering-Headrest-Eating-Writing/dp/B07Z92Y8JV/
YO! I'M ALSO IN CM AND WORKING NIGHT SHIFTS! Yaaaayyy
Not.
It sucks. It's so hard to live a normal life working nights, especially when I've got kids.
But - I'm doing it. I'm studying over the course of 6 months instead of 6 weeks. Little by little.
I take the PE in 2.5 weeks! Eeeek!
I also spend a lot of time working out of my "truck" on the construction site.
But honestly - I find it so hard to study in the dark, at 1 am, cramped in my vehicle. My brain is just... not at 100% in the middle of the night.
I study during the day after I wake up, like 1pm - 3pm, and then go work my night shift.
So, life is basically "night shift - study for exam - night shift - study - night shift - study", which sucks, but it's temporary.
We got this!
Only cheap thing I can think of is this for the driver seat https://www.amazon.com/dp/B07Z92Y8JV/ref=cm_sw_r_cp_apa_glt_fabc_4PVVADFWPFGE9FACGCV8?_encoding=UTF8&psc=1