I got a nice brass bell with my bike - it mounts as one of the headset spacers. Only trouble is that this means I need to take my hands off the handlebars to ring the bell. Oh, and it's kinda awkward to find the tinger thing.
On other bikes I've mounted the bell just under the brake hoods, within easy reach of my thumb. So I printed an adapter that would allow me to unscrew the bell from the headset spacer, and fit it to the bars instead.
It's printed in black ASA with 4 walls (i.e. solid and no room left for infill), and has an M5 brass heatset insert for the bell to screw into. It fixes to the handlebars with an O-ring mount.
The author marked this model as their own original creation.