UPDATE: Now available for the GPSMAP 78 series (scroll down for pics).
I received an email a couple of weeks ago from a fellow in Idaho who hand manufactures a new style of mount for the Garmin 60 series. It looked interesting enough that I agreed to test it out, and I came away pretty impressed.
Made from Concealex (a modified form of Kydex), the mount seems very rugged, and doesn’t appear to block GPS signals, allowing the unit to be almost completely enclosed. Dave Jankowsky, creator of the mount, has dubbed it the Buzz Bomb Cradle. You need to use a RAM diamond mount with it; I used the RAP-274U.