I am using a Garmin 496 in a panel dock. The 496 will get its power from a factory-supplied 12v power cord. This cord has a automotive-style 12v plug. I was advised to use the plug as it has an internal fuse, so I needed to install a female 12v receptacle behind the panel. I used a couple of padded clamps to mount the receptacle onto one of the support tubes.
I have a breaker on the panel for the GPS as well.