Harman Kardon makes a drive and play....model DP1US....Google it. They also make a color unit. I bought 12 units for $18- each on Buy.com last year. Had one installed in my 2008 IS250.....works great and looks great .
Google for what you are looking for and there are some units out there for about $200- that will work with your Navi screen. Saw on on Ebay.
Good luck.
Randy Wong