Recommendations for bells to hang from door for potty calls?

Trying to train our dog to ring a bell that's hanging from the door when she needs to go out, and she's getting the hang of it, but is just doing the most gentle of touches and the sleighbells we're using hardly ring. I'm worried I won't be able to hear it from upstairs or the other room. Any suggestions for bells that are easy to trigger and loud enough that it'd be obvious? thanks!