Here is the Arkon website. See if anything here will suit your needs. You should be able to get the mount here and fabricate a gooseneck using some flexible steel tubing ( like from a gooseneck lamp ). Building supply warehouses sell the flexible steel tubing and mighe even have the connecting ends ( brackets ). Arkon sells a kit with a 15" gooseneck. The bracket just bolts onto the gooseneck, so you might be able to make your own to fit your headrest or wall.
http://www.arkon.com/