This is something I've been looking into since driving a Ford Escape rental for work. GROM makes a add on unit that adds USB, Ipod, and a optional bluetooth audio module. I don't know if there is another option.
http://www.gromaudio.com/usb.html
The thing to keep in mind is that the add on is roughly $130 last time I checked on Amazon. If you have one of the more advanced head units in your versa it's probably worth the upgrade. If not swap the unit out for a 3rd party unit with these features.