BuddyPress.org

It’s not a HTML file, but rather a function that is located in /buddypress/bp-core/bp-core-adminbar.php.

What are you specifically trying to do?

If you’re trying to modify the BuddyBar, read this:

https://codex.buddypress.org/how-to-guides/modifying-the-buddypress-admin-bar/

Requires a bit of manual coding.

Or you can also try this plugin:

https://wordpress.org/extend/plugins/buddypress-admin-bar-mods/