Glad I read this.
I have been meaning to get a few spares of the Shimano Cantilever Link Wires ("A" and "B") for my Shimano CX-50 brakes. At $3.99 each, it beats all the fabrication here. For my setup (55cm frame), even the 330mm straddle wires would be pretty long. PLus once you suss out the adjustment process, they are actually easier to adjust than traditional straddle wires.