It seems that there is no way to turn SCP on in cli.....
So, I would try to sniff HTTP traffic::
- Download, Install and Run Wireshark to sniff HTTP traffic between PC and switch.
- Open webbrowser login to switch via HTTP and download config file.
- Analyze sniffed HTTP traffic and find the GET request that initiated download.
- Try wget/curl Linux utilities or write your own script (python/perl etc..) to download config the same way as your browserd do.
When (if) you succced, you can configure HTTPS on your switch and use HTTPS in your script instead of HTTP for security..