How can i get separate navigation links?

I am using this function to make my navigation a dropdown list

<nav class="page-name">
        <?php
            class Walker_Nav_Menu_Dropdown extends Walker_Nav_Menu{
                function start_lvl(&$output, $depth){
                    $indent = str_repeat("\t", $depth); // don't output children opening tag (<code><ul></code>)
                }

                function end_lvl(&$output, $depth){
                    $indent = str_repeat("\t", $depth); // don't output children closing tag
                }

                function start_el(&$output, $item, $depth, $args){ // add spacing to the title based on the depth
                    $item->title = $item->title;

                    parent::start_el(&$output, $item, $depth, $args);

                    // no point redefining this method too, we just replace the li tag...
                    $output = str_replace('<li', '<option', $output);
                }

                function end_el(&$output, $item, $depth){
                    $output .= "</option>\n"; // replace closing </li> with the option tag
                }
            }

            wp_nav_menu(array(
                'theme_location' => 'primary', // your theme location here
                'walker'         => new Walker_Nav_Menu_Dropdown(),
                'items_wrap'     => '<select>%3$s</select>',
            ));
        ?>
    </nav>

But I cant use the pages names to navigate because they are unaware of the formatting of the links that can look like this: /?p=57
How can I get the the href value that is generated in normal nav menu and put it as a value attribute of the <option> element?

Also, how can I display current page name in the select box?