In Black Panther (2018), the following event happens
After ingesting the heart-shaped herb, Killmonger orders the garden to be burnt, leading to all the herbs getting destroyed except one. That one is consumed by T'Challa. Hence, as far as what we know, no heart-shaped herb is left. And no other way of gaining Black Panther's powers is shown in the movie.
Given that, has there ever been any mention in the comic universe of an alternative way of becoming a Black Panther?