you dont actually need one that works with you 2012. anything will work.
think of it this way. your pathfinder screen is no more than an ordinary TV. nothing special about it. Nissan made their own display and connected it to the screen. what you will do is add a DVD (any normal DVD player that works over 12V) and a NAV module.
you will need to install a 3-position switch to switch between the inputs you have:
1- nissan A/C controls
2- DVD
3- Navigation
sample switch: (i know its ugly for a car, but im just using it to demonstrate the idea)
let me know if this isnt very clear, i'll draw you a diagram on how it will connect. also we have a few threads on here with people that already did this. search this forum for "DVD" and check the builds.