Not a DVD solution but I just bought an iPad headrest bracket, attached it to passenger seat headrest. Insert ipad (or any tablet, one we bought is universal fitting) and you're done.
Bracket fits well and bonus is when you get where you are going just take iPad out and use at destination. With the rise of tablets and now decent brackets I really cannot see DVD rear entertainment options surviving much longer. Now I just need to find an app that will let my wife control said iPad from her front seat using Bluetooth to save her having to reach around whenever he wants program changed