I took a twist tie and removed the plastic, to see how thick it would be and if I could get bendy with it and not have kinks. Could work?
If you are going to use wire I would suggest florist wire, the thin stuff is really easy to shape. As soon as I found my mother in laws stash I nicked some for spears etc and thin stuff as pins and industrial effects.
Thanks to all for the swift and helpful responses. I guess I'll just have to get a very fine drill and and proceed by trial and error. At least now I know to attach the reins to the yoke and not the muzzle.