The bubble has no logic, you need to use the accessory for the leader. So, use the MapView delegation method:
- (void)mapView:(MKMapView *)mv annotationView:(MKAnnotationView *)pin calloutAccessoryControlTapped:(UIControl *)control;
And add a leader in viewForAnnotation delegate mode. For instance:
UIButton *myDetailAccessoryButton = [UIButton buttonWithType:UIButtonTypeInfoLight];
myDetailAccessoryButton.frame = CGRectMake(0, 0, 23, 23);
myDetailAccessoryButton.contentVerticalAlignment = UIControlContentVerticalAlignmentCenter;
myDetailAccessoryButton.contentHorizontalAlignment = UIControlContentHorizontalAlignmentCenter;
pinView.rightCalloutAccessoryView = myDetailAccessoryButton;
, .