Nordost is good for the money. Kimber used to make a flat cable, but I don't know if they still do. I use Kimber 8TC with my B&Ws, but I guess that won't work for you.
Have you thought about the Electra Glide speaker cables? They use custom flat ribbons from Alpha Core Goertz.
Have you thought about the Electra Glide speaker cables? They use custom flat ribbons from Alpha Core Goertz.