Guys!! Just check the link below!!
My GX doesn't come with the RSES, but I want to watch DVD on Nav so badly, it enabe the driver to control play, Pause, FF, REW, and stop on the Navigation screen!!
However, I searched on the web, but no clue where to buy that!!
CD/DVD Changer

 

As you saw in the discussion this is LX FACTORY DVD changer.. you CAN get them but they are around $1000 ... I believe a guy was posting that he can get them (on lexusowners forums...) ... dunno... you want to make sure you have the harness for it though I am sure its compatible with the NAV software but they key here is the harness... my understaing is that the GX might be prewired for the DVD Player in the console so the harness might be compatible but it won't be long enough to reach into the trunk.. .ask the guy in the thread maybe he can help you

 

I'm guessing the our Navigations have the ability to play DVD with the OEM DVD changer if we could unlock the function. With the RSES, it could play movie just like that.
But still, I think the aftermarket parts such as nav-tv.com is kind of messy because remote control is needed to play. Another one is vaistech.com(available in the summer), it costs about 700 and + a DVD player. It's like the same price...