List only sub-directories containing two specific files

I'm running the following code on iOS using my iPhone's terminal, to be clear, this command is run within my jailbroken iphone using a slim terminal tweak called New Term 2:

cd /var/mobile/Library/Widgets
find . -maxdepth 3 -name 'index.html' -printf "%h\n"

This returns the list of the folders containing index.html. I'd like to know how to add another file: Config_extra.js (if it exists, it'll be located in the same folder as index.html) to the search in a way that the results show **only folders containing both files** Thanks in advance