There are other pencils. You do not need them. You just need a P205.
There is a good chance you have used a Pentel “Sharp” series mechanical pencil before. They are cheap (five bucks?) and widely available. I have spent hours using a P205 to solve problems, take notes, and doodle mindlessly. I have been using the same Pentel Sharp P205 for over a decade. Here is why:
The P205 does not ask for my attention, it just does the job. It is practical- just a bit of black plastic and metal where appropriate. There is also a tiny eraser. Is the P205 brutalist? It is a pencil.
It seems to hold and advance the lead in an appropriate way and I can not remember a time that I felt uncomfortable holding it. As for the tiny eraser, mistakes are uncomfortable. Is that a bad thing?
The “5” in P205 indicates that it uses 0.5mm leads. There are also P203,P207,P209 models. In my experience, 0.5mm is the right size for everyday writing and diagraming.