Here is a good source for 12awg true shielded milspec tinned copper twisted pair. You dont have to ground the shielding but it is there if you want to. Also below is another good source to get high quality wiring and connectors. Yes it is probably over kill but its something I dont have to worry about after its installed
https://www.ebay.com/itm/M27500-12TG...QAAOSwBJxeU~OF
https://prowireusa.com/c-59-m22759-32.aspx
https://prowireusa.com/c-32-m22759-16.aspx