There is such a thing Steve, I have seen it. Not sure what option it was, but I know Kev had one in his JDM roadster.
Edit: A quick search suggests Alex may have some (well, he did in 2013 ) http://www.350z-uk.com/topic/67633-2003-06-retractable-cubby-sat-nav-model/
Seems they are quite elusive.
Found this video of one in operation though, and looks very good.