This may sound dumb, But the little horn on my Shadow 1100 doesn't deter anyone. Would I require an extra battery to operate a semi horn if I attached it to my bike. Is this just a bad Idea over all? Don't be afraid to criticize my idea.
Great idea but it would never work. Unless you have an air compressor on your bike to run the semi horn. They are powered by air, which gives them the name "airhorn". So your best bet would to be just learn to live with your problem or check with a motorcycle dealer and see it they have any solutions. Sorry!