It appears this may have already been modified in an attempt to fix the horn - I've never seen the wire attached to the horn button before. There is a tube that should be part of the horn connection that is broken off your horn ring/cancel cam:
Just before the final assembly you would put a spring and then the plunger pin into the tube
If there are no junkyards close by, I would think that you would be able to get the parts shipped to you fairly cheap, they are small and light, and as mentioned above, they were used in lots of different columns so should be quite plentiful.
[This message has been edited by NetCam (edited 08-03-2012).]