I opted for the Stebel but had thought about a car horn off of a similar car. I would have used both the high and low with a relay triggered by the original button but liked the air horn idea better. The idea is to be heard so either way works fine and the car horn will probably last longer.

I learned all I need to know about life by killing smart people and eating their brains.
Eat right ,Exercise ,Stay fit, Die Anyway!