Originally Posted by
Giro
Corrected link to
Wollo electric motorcycle horns. Of the available sound samples, their MODEL 225-2T / 115 Decibels-420/510 HZ sounds the best to me but it looks heavy (though maybe not compared to the battery that might be required).
No kidding! The smallest horns draw 4A (!!) at 12V - better not use it too much!