12V car horns are a bit heavy and use 18-30A (eg. the Screaming Banshee) to run so aren't a good solution on a bicycle.
OTOH, a single-tone, 12V motorcycle horn uses much less current (1.5A) but sounds feeble and not anything like a car horn.
Also, to complicate matters, li-po batteries for use on remote-controlled toys aren't available in 6V or 12, but rather 7.4V or 11.1V formats. But then, 12V lead batteries are big and heavy.
So I was wondering if someone knew of a good compromise in terms of weight and current for use on a bicycle.