+1 for wacom tablets. Been using them for around 10 years instead of mice, for the ergonomic benefit. Portable, and cheap (bamboo series 2nd hand). Last several years each, too. Also native Linux support.
Two questions: 1. How do you scroll ?! 2. What Wacom tablet do you recommend?
Some Wacom's come with a scroll wheel. Some double as touchpad, so it can quickly be used as a touchpad.
I was using the medium, non-pro Wacom's (Bamboo) and these were just as good as the pro versions. Also, it is a great entry point than jumping full-in to the higher-priced models.