Dave Brown Products used to sell that sort of stuff. I've seen CF extrusions (rod and flatbar) in the LHS. Not sure it was K&S, but it was near the K&S rack of tubing, rod, sheet brass, etc. Otherwise, I'd look at CST or Tap Plastics websites and see if they have it.

Steve
Edit: Dave Brown Products sold everything except the spinners & adapters to Ohio Superstar Products last year. I can't believe they didn't tell me! The CF tape is still available, but apparently not in multiple thicknesses. You start at the end and snap it to the correct width, then keep it going down the length you need. Use CA to glue it, not epoxy, of course.
http://www.ohio-superstar.com/dave-brown-product-line/carbon-fiber-strip