Extending Footer Contact Info Widget

I would like to add a couple of more custom lines to the Fortuna Contact Info widget. How would I extend this to create my own version in a child theme. I found the code I need to extend in fortuna/includes/boc_widgets.php but I don’t want to do it there and have it get overwritten in the next update.

I’d like to copy and re-name that piece of code that begins
class contact_info_widget extends WP_Widget {

Duplicate it somewhere in the child theme and re-name and extend it and have it get initialized and see it in the Widgets section as a new widget. Do I create a new functions.php file in the child theme to do this? Can I use an includes/my_widgets.php file in the child?