I have the Goertz Alpha Core MI-2 cables. Goertz is owned by Bridgeport Magnetics and I have purchased zobel networks directly from them for using with the MI-2 cables. I think to purchase from Bridgeport you need to phone them.
Last I checked the Cable Company also sells them. Depending on your amplifier you may want to use zobel networks with the cables. They are simple little four inch or so wires that may be built into the cables nowadays.