The simply-named Oi, made by Australian cycling gear company Knog, is a bike bell for people who don't like bike bells. Such folks may be particularly keen on the latest model, the Oi Prima, as it's sleeker, slinkier and better-functioning than ever before.
Or grab a Crane E-Ne which is pretty small yet loud and clear:
I have one that’s even smaller, but still very loud. I forget who made it but it just says “made in Japan” on the center of the bell. I wanna say it was the Osaka Bell Co.?