Hi Barry,
Thanks for using our plugins. I can try to help out here.
I looked up the function and found this two functions.
echo Tribe__Events__Main::instance()->esc_gcal_url( tribe_get_gcal_link() );
echo esc_url( tribe_get_single_ical_link() );
You could add those to the ticket template:
the-events-calendar\src\views\tickets\email.php
To display the links after you follow the themer’s guide to move that template to your theme:
https://theeventscalendar.com/knowledgebase/themers-guide/
You can pass the event id to both I believe.
Those functions only provide a link so you will need to add them inside your html tags.
Cheers