Well, you should understand that 3D art requires a good measure of time, energy and sometimes money. Not just the actual work, but the research it takes to pull it off. Even for an experienced developer, to create a scene large enough to provide reasonable amounts of data like that will take a lot of work. It’s unlikely someone would want to simply give their scene to someone because of how work intensive it can be. Especially for a fairly realistic scene. Unless of course you pay someone, they might consider it.
In the meantime, why not check out some City generators and create a procedural algorithm. That might actually be worth doing. Instead of acquiring a single static scene, a city generator can create different set-ups by simply changing the recipe (or inputs). This way you can perform a variety of tests. It will still require a manual effort to add “realism” to the scene. A city generator can create a layout for you, but you still need to set-up materials, lighting and what not.