To my understanding, the 02 aurora had an option of navigation. What is the best way of locating it and do you simply swap out the current radio and have navigation?
You could try eBay or craigslist…failing that, a dealer can probably get one for you.
However, any of those are likely to be more expensive than simply purchasing a standalone GPS unit (such as a Garmin), not to mention the additional costs of installing a factory navigation unit.