This function enables products and other post types in Divi Search Module.

/* enable Products and other post types in Divi Search Module BEGIN */
function custom_remove_default_et_pb_custom_search() {
	remove_action( 'pre_get_posts', 'et_pb_custom_search' );
	add_action( 'pre_get_posts', 'custom_et_pb_custom_search' );
}
add_action( 'wp_loaded', 'custom_remove_default_et_pb_custom_search' );

function custom_et_pb_custom_search( $query = false ) {
	if ( is_admin() || ! is_a( $query, 'WP_Query' ) || ! $query->is_search ) {
		return;
	}

	if ( isset( $_GET['et_pb_searchform_submit'] ) ) {
		$postTypes = array();
        
		if ( ! isset($_GET['et_pb_include_posts'] ) && ! isset( $_GET['et_pb_include_pages'] ) ) {
            $postTypes = array( 'post' );
        }

		if ( isset( $_GET['et_pb_include_pages'] ) ) {
            $postTypes = array( 'page' );
        }

		if ( isset( $_GET['et_pb_include_posts'] ) ) {
            $postTypes[] = 'post';
        } 

		/* BEGIN Add custom post types */
		$postTypes[] = 'product';
		/* END Add custom post types */

		$query->set( 'post_type', $postTypes );

		if ( ! empty( $_GET['et_pb_search_cat'] ) ) {
			$categories_array = explode( ',', $_GET['et_pb_search_cat'] );
			$query->set( 'category__not_in', $categories_array );
		}

		if ( isset( $_GET['et-posts-count'] ) ) {
			$query->set( 'posts_per_page', (int) $_GET['et-posts-count'] );
		}
	}
}
/* enable Products and other post types in Divi Search Module END */