I picked up a Targus laptop power adapter a few years back... can't find it with quick search - but it had both a 110v and 12v option to power the laptop - and tips to fit almost anything...
When boondocking I power the laptop directly from the 12v (cigarette lighter)... More efficient that converting 12v DC to 110v AC for the PC power supply to convert it back to DC...
You would just need to add a cigarette lighter socket where desired.
I did find the 12v only version of it:
https://www.amazon.com/gp/product/B00365EE2G