I think I've found it.
Costs as much (or as little) as you choose, highly customizable, keeps track of all the bits and pieces of everyday errands, even has space for doodling and scribing down story ideas. And it doesn't plug into anything or have a battery life. Thank you, Ryder Carroll!
I've only been using my particular cheapie bullet journal (a quad-rule paper composition book) for a few days, but I'm liking it a lot. And I am successfully Getting Stuff Done, which is a huge boost.