Rube Goldberg, eat your heart out. I had already purchased something from Origin 8 but I couldn't wait. I was rummaging around the parts bin when I came across an old bike reflector mount. In fact I tried two other ones first but they didn't do it for me. This one did.
If this doesn't hold out, Plan B is to modify a Canti brake bridge by drilling a hole at the top and mounting another makeshift cable hanger.
This solution works nicely