Get Previous Post based on Custom Field Name, for Custom Post Type

I am using this query but the results returned are based chronologically (from my understanding) for get_previous_post().

   <?php $prevPost = get_previous_post();
          if($prevPost) {
              $args = array(
                  'posts_per_page' => 1,
                  'post_type'     => 'brands',
                  'meta_key'    => 'br_type',
                  'meta_value'  => 'Fashion',
                  'order'       => 'ASC',
                  'include' => $prevPost->ID
              );
              $prevPost = get_posts($args);
              foreach ($prevPost as $post) {
                  setup_postdata($post);
      ?>

<div id="apostnav" class="kfocon"><a class="aplink" href="<?php the_permalink(); ?>" title="<?php the_title(); ?>"></div>

   <?php
                  wp_reset_postdata();
              } //end foreach
          } // end if

I am looking for code that will fetch the previous post based on the alphabetical order of custom field br_name. How could I do this please?