I look at these things and the Model 100 is just about the minimum size I would use.
First, it has to be designed around a real (non-tenkey) keyboard, with a 25- 40- whatever-line screen chosen for size. That is the minimum footprint. Then stuff everything else underneath this top in as thin a manner as possible, of which the CPU and its cooling would probably be the thickest component.
I'm skeptical that anybody needs these tools to fit in pockets.