How to set custom scrollbar for the megamenu in mobile mode ?

Hello; I am trying to set a custom scrollbar for the meganemu when it is in mobile mode. So normally with t3_blank, when click the icon in top left corner, the megamenu expand and the browser scrollbar appear. This is not an issue but browser scrollbar differ from browser to an other which can modify the look and feel of visitor. For that i made a decision to change the default browser scrollbar into a mush elegant one, the best i have found is here jquery-custom-content-scroller. And i still didn't manage to make it work for the megamenu, i have included the javascript, css and image as expected into the root folder of website (in localhost right now, to speed up the testing). And i did the following :

    (function($){

        $(window).load(function(){

            $(".t3-megamenu&quot.mCustomScrollbar();

        });

    })(jQuery);

And this one also :

jQuery(document).ready(function() {

jQuery(".t3-megamenu&quot.mCustomScrollbar();

});

None of them work, i wouldn't like to touch nav-collapse or collapse classes because those are bootstrap related and may cause the function to apply for something else not megamenu.
If someone know how to make it work, please share it here.
Thank you.