IonButton and IonBackButton customizations

I would like to prompt a confirmation alert when my user clicks on IonBackButton.

I could not see any way to do that.
Therefore I thought I would rely on a custom IonButton:

            <IonButton onClick={askConfirmation()} >
              <IonIcon icon={arrowBack} />

However the buttons do not look the same:
(left: IonButton, right: IonBackButton)

Applying a custom css seems to do the trick:

.my-back-button-class ion-icon {
  font-size: 24px;

But seems hackish and probably not very scalable.

What is the cleanest way to achieve my goal?