Giving contributors/authors access to commenter email

Contributors and authors on our site need to be able to see the email addresses of commenters. I’ve made a change in class-wp-comments-list-table.php, that allows this, but of course that change will disappear when I next update WordPress.

Can anyone point me in the right direction so I can make the change in my functions.php or as a plugin.

BTW: I’ve tried a couple of plugins, like Adminimize and Capability Manager, that don’t do this.

Thanks for your time.