I have added this function by amending the file below as follows:
/anchor/models/page.php
/*
//Original query
$query = static::left_join(Base::table('users'), Base::table('users.id'), '=', Base::table('posts.author'))
->where(Base::table('posts.status'), '=', 'published')
->where(Base::table('posts.title'), 'like', '%' . $term . '%')
->or_where(Base::table('posts.html'), 'like', '%' . $term . '%');
*/
$query = static::left_join(Base::table('users'), Base::table('users.id'), '=', Base::table('posts.author'))
->left_join(Base::table('post_meta'), Base::table('post_meta.id'), '=', Base::table('posts.id'))
->where(Base::table('posts.status'), '=', 'published')
->where(Base::table('posts.title'), 'LIKE', '%'.$term.'%')
->or_where(Base::table('post_meta.data'), 'LIKE', '%'.$term.'%')
->or_where(Base::table('posts.html'), 'like', '%' . $term . '%');
Hope this can help others.