Hey Daniel,
It isn’t possible without customization, unfortunately, but if you’re comfortable with adding custom code you can definitely do this. Our themer’s guide here is a great place to start → https://theeventscalendar.com/knowledgebase/themers-guide/
To add the purchase button, your best bet is to dive into the actual plugin code of whichever Ticketing Framework you have, and see how the “normal” buy now buttons are generated on the single-event view.
Does this information help? Let me know!
— George