Show site categories in dropdown that shows Pro sites


On the mainsite on my multisite, I am showing the latest Pro and Elite posts (level 1+2 created from Pro Sites), with a sorting option at the bottom. I have now added a category option, because I want users to be able to choose their favorite site category.
Right now it uses the categories of the mainsite, and I do not want that. I want it to show the categories from WPMU's Site Categories plugin. I want to keep the styling of the posts on the frontpage, and do not want to get a new looking page with a list design.


The code I am using for the category dropdown right now is this:

<li>    <form id="category-select" class="category-select" action="<?php echo esc_url( home_url( '/' ) ); ?>" method="get">
        $args = array(
            'show_option_none' => __( 'Vælg kategori' ),
            'show_count'       => 0,
            'orderby'          => 'name',
            'echo'             => 0,

        <?php $select  = wp_dropdown_categories( $args ); ?>
        <?php $replace = "<select$1 onchange='return this.form.submit()'>"; ?>
        <?php $select  = preg_replace( '#<select([^>]*)>#', $replace, $select ); ?>

        <?php echo $select; ?>

            <input type="submit" value="View" />