Lexus LS430 2002 interface for backup camera ?

Hi,
I want buy interface to allow backup camera (or two) to be connected to OEM navigation screen of my LS430 2001 - European version.
Can you recommend any your product ?
I have external monitors in headrest with separate DVD so I'm not interested to add more video sources to navi screen.
Thank you,
Mariusz
p.s. can you explain what is GVIF output ? I saw on electric diagrams only RGBs in/out from navigation unit to screen on dash.
I want buy interface to allow backup camera (or two) to be connected to OEM navigation screen of my LS430 2001 - European version.
Can you recommend any your product ?
I have external monitors in headrest with separate DVD so I'm not interested to add more video sources to navi screen.
Thank you,
Mariusz
p.s. can you explain what is GVIF output ? I saw on electric diagrams only RGBs in/out from navigation unit to screen on dash.