I took the line from your example.
But you probably need to pass the second parameter with the class name prefix.
Sample code from my live, working app:
PHP Code:
$viewRenderer = Zend_Controller_Action_HelperBroker::getStaticHelper('viewRenderer');
$viewRenderer->initView();
$viewRenderer->view->addHelperPath(APPLICATION_DIRECTORY . '/views/helpers', 'My_View_Helper');
Example helper class name is class My_View_Helper_ContactSelect for the helper 'contactSelect'
According to the API Docs,
Docs For Class Zend_View_Abstract, the second argument defaults to Zend_View_Helper