About bell designs-
I have a no-name bell that I bought with the hybrid bike at the LBS years ago. It has a little handle I push (sideways) with my thumb, and it goes: "RRRRRRRINNNNNNNG" It's like the bells of the olden days - there's a spinning ringer inside.
I've bought-online- a couple of bells recently that I don't think will be nearly as useful, so I still haven't put them on my other (bell-less) bike.
Both of those bells are the type where you move a lever and release it and the bell goes: "DING".
One is a 'SAFER' (Made in UK) bell and the other is the Spurcycle knockoff. I wouldn't recommend either unless you enjoy flipping a lever again and again with your thumb.