WooCommerce: products search form using a custom template file
<?php
$form = '<form role="search" method="get" id="searchform" action="' . esc_url( home_url( '/' ) ) . '">
<div>
<label class="screen-reader-text" for="s">' . __( 'Search for:', 'woocommerce' ) . '</label>
<input type="text" value="' . get_search_query() . '" name="s" id="s" placeholder="' . __( 'My Super Search form', 'woocommerce' ) . '" />
<input type="submit" id="searchsubmit" value="'. esc_attr__( 'Search', 'woocommerce' ) .'" />
<input type="hidden" name="post_type" value="product" />
</div>
</form>';
echo $form;