If you were really adventurous though, you could in theory... Use desktop components...
I'm talking really low power draw stuff... Mini-ITX ITX Micro-ATX low low wattage everything...
Make your own case for the motherboard and monitor in a briefcase style, and find a way to hook a decent battery to it, **** maybe even some solar panels >
And a small as possibly PSU.
You could in theory build a "laptop" though it would probably be quite bulky, if you did it right, you could make it way more ****** than a conventional laptop.
Keep in mind that would by a DIY build from the ground up.
Only do it if you're really really serious about building your own.