Volvo V90 Wagon's horn does not work

Suddenly, the horn on my '97 Volvo V90 (wagon - really a 960 wagon) stopped working. The mechanic checked out connections. The only thing he came up with was to get inside the column and see if a wire had come loose. Not only is that wildly expensive, but the air bag issue is a big deal. Finding a junk yard with a wheel, horn and column is impossible for this model. I have to pass inspection soon. Any ideas for testing in and around the column? And, if after all testing is done, what are the options??

There is a fuse and a couple relays. The horn relay and the overload relays. The horn fuse and relay are under the hood. The overload relays are driver side dash. You can swap the relays and fuse with one like it, same part number and or rating. Once you have done that you can check the frame ground for the horn. Just make sure it is free of rust and making good contact.