[fw-mvc] Bootstrap Resource usage in model - best practice advice please

This is probably a dumb question, but I'm looking for a way to call a
bootstrap resource from a model (in this case is a Zend_Cache object).

Bootstrap method:

protected function _initCache()
{
$frontendOptions = array(
'lifetime' => 7200, // cache lifetime of 2 hours
'automatic_serialization' => true
);

$cachedir = realpath(/path/to/cache');
$backendOptions = array(
'cache_dir' => $cachedir
);

$cache = Zend_Cache::factory('Core',
'File',
$frontendOptions,
$backendOptions);
Zend_Registry::set('Zend_Cache',$cache);
return $cache;
}

Obviously this is set into the registry so I can access it that way, but
I was wondering if this is the best way to do it, or whether there was
some way of calling it like you do in a controller:

$this->_cache = $this->getInvokeArg('bootstrap')->getResource('Cache');

or maybe even passing it directly over to the __construct of the model.

Any advice greatly appreciated