GN032+WPCS2: i.Trek Bicycle / Handlebar Mount & Case for Garmin, TomTom, Magellan GPS with 4.3" or 3.5" screen
I use one of these to hold my GPS and one to hold my map.  Good item to have for your handlebars, only issue is the zippers are a little hard to pull sometimes, and the glare on the plastic window, from the sun.  I could live with the zipper issue, but would like them to work on the glare issue.