If you’re looking for a truly budget option, we doubt you’ll find anything better or cheaper than the LifeLine Bike Bell. Made from a lightweight (26g) rustproof alloy with a plastic hammer and fixing, this one attaches to your bike bars via a cable-tie style strap that makes it easy and quick to get on and off.
It’s an unobtrusive little thing (it’s about the size of a thumb) but for its size it emits a high-pitched ring that’s certainly loud enough for pedestrians (and dogs) to hear. It’s also available in a wide variety of colors including black, green, blue, red, gold and silver so you should find something that’ll complement your bike’s color scheme. And at such a low price you could probably afford to buy a few!