The classic way was to dump memory while in the desired city (usually by using classic .dat browserhax, fixed in 9.5 or something), isolating the appropriate part of memory, then restoring it while in your city and save
The basic principle is theoretically still applicable (for example through Rosalina debugger), though I don't know how to identify the right area of memory - or for that matter a good memory editing client for GDB
If all else fails you can go to an ebay mercenary for 80 bux
