You can get Navi chips in the slot in Netopia near the Hotel and Bank. Choose ten chips in the slot and get a new Navi chip back free. Sometimes you can even get Version 2 Chips. Note: A Navi chip does not appear every time.

Defeat Freezeman, then go to ACDCtown. There will be a chip trader by the posters. You will get all the Navi chips except Bass and a few other that you can get only in the WWW area.