Input devices for your plotter
You will need some kind of input device (mouse/pointer/trackpad/touch/keyboard) for your system. There are many options.
Some opt for a touchscreen display. But in my experience, even the good ones suck to use with wet and cold hands. The waterproof ones are also expensive.
If you want a touch option, you can get cheap second-hand rugged tablets. We got a used Samsung Galaxy Active Tab 2 for 80 EUR that we use for all kinds of things onboard. It has been very useful and could potentially serve as a touchscreen for the [Raspberry Pi]https://sailingcourage.xyz/other/what_is_a_raspberry_pi/.
If you go for a non-touch screen, you need some kind of mouse. Commercial ships normally use trackballs. But waterproof ones are not widely available. A waterproof silicone mouse is a good substitute.
I initially got one with touch zoom scroll. But I changed to one with scroll buttons, because they work better when wet.