Hey Dan,
Thanks for reaching out!
This “sponsors” field you are referring to is not anything that our plugins generate themselves, and so it must be coming from some other plugin on your site or from your theme.
So, yes—you will unfortunately have to custom-code some version of this to work with events.
We unfortunately cannot help with customizations, so I would recommend that you reach out to the plugin author whose plugin adds these fields to see if there is a simple way to go about adding these fields to Events. It may be possible to just add the features to custom post types; if so, the post type slug for Events Calendar events is tribe_events.
Cheers!
George