I've been using
this Coodio cover on my Glo HD but in a medium shade of blue (which I can't find available anywhere again). The size of the Glo and Glo HD are similar enough that all of my older Glo covers fit the Glo HD.
I recently switched to
this cover though since I really like the darker blue. The actual cover is slightly different than the picture shown, it doesn't have the usual small lip sticking out for the magnets on the side, rather it's a straight edge where the magnets are and adds very little width to the cover.