I found the following link to the company that makes the system for the G35. I don't know if you can buy the system separately from them or not, but from the pictures on their website it looks like you could. No idea how hard that would be to retrofit into the G35 if you didn't order it from the factory that way. My local dealer has had only 1 car with Nav and he said that was a customer pre-order that they weren't ordering any cars with Nav as part of their alotment because they are too hard to sell. ???? Geez, that happens to be what we are looking for. Go figure.

http://www.xanavi.co.jp/e/products/index.html