Try signalcable. Around $60 +. They claim these cords are used as stock in $15K Velo sub.
http://www.signalcable.com/
http://www.signalcable.com/
Subwoofer Power Cord Suggestions
I'm looking to spend up to $600 used for a new power cord for my Rel subwoofer. I'm looking for suggestions on where to start. Please let me know what PC are you using and why do you like it on your sub? I like bass that is well defined with plenty of texture. Much Appreciated!