Hope this code may work for you.
$query1 = new WP_Query( array(
'post_type' => 'product',
's' => $searchStr
));
$query2 = new WP_Query( array(
'post_type' => 'product',
'meta_query' => array(
array(
'key' => 'my_meta_key',
'value' => $searchStr,
'compare' => 'LIKE'
)
)
));
$result = new WP_Query();
$result->posts = array_unique( array_merge( $query1->posts, $query2->posts ), SORT_REGULAR );
$result->post_count = count( $result->posts );