Night City is the hometown of Cyberpunk. Most use it as a campaign-setting. Since the Night City Sourcebook is no longer available, most don’t have a map. But you need one – I can tell by the amount of people asking google for a “night city map” and then being send here.
RTG hasn’t allowed to republish the original map, so I can’t help you there. BUT on the web there is one map that shows greater Night City, which might help you. It can be found here. Another Map reminds me very closely of the city center, but might be just the one from the main sourcebook, which you probably already have.
But there are a lot of sites out there with other, less fictional cities, making them useable for a cyberpunk campaign. I’m going to list some and would ask you to add any other you know in the comments.
- New Tokyo
- Verona Beach (as seen in Romeo & Juliet)
- Police State
- Los Angeles
- New York
- Dallas/Fort Worth
Or you play on Mars.