There are no GPS's that will share the chart card with your C80 so you can't captilize on that. The best thing to do is buy a cheap gps that you can store on your boat with some spare batteries. I would suggest the Garmin GPS12. You can put waypoints on it that will get you home easily.[*]
Garmin GPS-12[/list]Of course if you think you will use the handheld GPS for other times like hiking or someting then you might look at a GPS with Maps. If that's the case let me know.