Getting "TypeError: $ is undefined" when calling drupal_add_js on an external file

Question

I am getting "TypeError: $ is undefined" in Firebug when I call the drupal_add_js on an external jQuery file. If it were some local code, I would just wrap the code in a behavior function, like so:

(function($) {
    Drupal.behaviors.addStuff = {
     attach: function(context, settings) {
       // jQuery code goes here.
     }
    }
 };

I know that I'm supposed to change the dollar signs to "jQuery." but I can't do that to an external file (since I can't edit the code). How do I safely include this file? Note that this is just one module, I do not want to add it to my template file, and I do not want it to run on every page on my site.