It’s going to be a custom code solution, one way or another, as there’s no built in way to do that now, from what I’ve heard and seen. If there is, I’m willing to be wrong ??
That said, some questions
1. is this author going to have standard blog posts as well that need to be able to be seen in an author archive? If no, then this snippet should help out:
function wpse107459_add_cpt_author( $query ) {
if ( is_admin() || ! $query->is_main_query() ) {
return;
}
if ( $query->is_author() ) {
$query->set( 'post_type', array( 'YOUR_CUSTOM_POST_TYPE' ) );
}
}
add_action( 'pre_get_posts', 'wpse107459_add_cpt_author' );
2. How important is the URL permalink? Asking this one because it likely could be possible to set up a custom query on some page or so, to include extra data like posts from this post type and a found author.