Roger for a laptop power supply look here --
http://store.yahoo.com/shopbattery/index.html
We have been coastal cruising with that set-up[laptop below - paper on deck] for years. Now that we are getting ready to take off full time wife asked that I repeat chartplotter in cockpit so I bought a weather-proof 10" color display that will mirror the laptop display. Don't know how it works have not installed yet. But it also means can watch movies in the cockpit without bringing the laptop up
.
Re mono vs color issue in the past was brightness and contrast -- that has been fixed. Color tells you more at a glance so if you can justify the $.
BTW if you're going with some new Furuno stuff most of the radars are chart plotters already that may solve the issue.