Jquery-Selector is to specific (input vs button)

the JQuery selector for finding the "Start upload" button is searching for an "input"-element. We are using "button"-elements on out site, so the selector doesn't work. I think a more general selector would quite be good here:

var $submit = $(this).closest('.filefield-source-plupload').find('input.form-submit');
var $submit = $(this).closest('.filefield-source-plupload').find('.form-submit');