Do you have an Android phone with Wi-Fi support?
If so, here's another option:
- Get a large MicroSD card for the phone, some support up to 32GB.
- Install the App SwiFTP server (free) and configure a username & password.
- Plug in your phone with its USB cable and enable Media Transfer Mode.
- Ensure Wi-Fi on the phone is enabled and start the SwiFTP server app
- To access via Wi-Fi, enter the FTP address in the Windows Explorer location field.
- Enter the username & password you provided and you're in.
If all goes well, you can transfer files/folders to the phone via USB on the PC it's connected to as well as transfer files/folders with the phone via Wi-Fi from any other computer.
If you need to map as a drive-letter over Wi-Fi, get NetDrive (also free).
The following shows an example of this working on my computer, i.e. left Window open directly from USB and the right Window open over the Wi-Fi share. When I added "A Test Picture.mp4" to the left window, it automatically appeared on the Wi-Fi path:
Alternatively if you don't want to use your phone (or is unsuitable), pick up a cheap/second hand Android Wi-Fi enabled phone with a MicroSD slot. Despite "The Internet" appearing in the location bar, this does not depend on the Internet and will work without Internet access.
See also mciahel's suggestion above.