Do you have a ziplock bag you can throw over the whole deal in case of rain?
Yes and no. I unplug the gps and remove it from the cradle, put it in a ziplok baggie (ziplok down), then put the ziplok part thru the cradle at the bottom and snap the gps back it place, plug it in and zip it up. I find it better this way b/c I can pull it taut in front so the screen is easier to read. It sounds weird, I know. I'll see if I can get some pics of what I mean.
edit: I don't worry about covering the power socket. It's not the standard cigarette lighter. It's o-ring sealed to keep the rain out when in use.