Are you serious? I ran 8 gauge wire for my stove when remodeling the kitchen and that stuff was a bi%#* to wrap around corners make connections with. I can't imagine hooking 6 gauge cable to a speaker or an amp terminal. That being said, try your local hardware store.
A pair of Straightwire Black Silc cables is listed here (not mine). It's nearly as stiff as the 8 gauge cable. Good luck.
A pair of Straightwire Black Silc cables is listed here (not mine). It's nearly as stiff as the 8 gauge cable. Good luck.