Most elegant solution to add rear brake cabling to a track frame?

saw a picture of a rear brake caliper located on the chain stay bridge (in porn between all the bitching), with some finesse that could be made to look tidy & inconspicuous.

Actually I have thought about that! I have an Aero Gran Compe brake left over which is tiny, but it is still not tiny enough as the frame is extremely tight (see above).