Query custom post types by meta field in a term from custom taxonomy

Assuming that the query works and you get all posts with ss_category terms (instead of those with ss_aff_category = true only), I think this should work:

$args = array( 
    'post_type' => array('advertisers_cats'),
    'posts_per_page' => 9,
    'tax_query' => array(
        array(
            'taxonomy' => 'ss_category',
            'terms' => array(100, 101),
            'field' => 'term_id',
        )
    ),
    'meta_query' => array(
        array(
            'key' => 'ss_aff_category',
            'value' => true
        )
    ),
    'orderby' => 'rand'
);

Note that I changed showposts to posts_per_page. You can also add 'post_status' => 'publish', to exclude concepts and trash items.