I've been using a cute bird shaped one because I thought my kid would enjoy it:


Pretty unhappy with it, though. If it rotates too far forward and touches a cable, it doesn't work. If you don't pull the handle all the way back before letting go it also doesn't work, bird's head stops before reaching the bell. I guess the spring is set to keep the head off the bell to prevent unwanted sound on bumps or something, so it has to overcome that.

Even worse, the bell slides around on the handlebar because the only spot I have free for it isn't a perfect cylinder (thus the zip tie trying to fix it in place horizontally).