disable (or add class) to a checkbox within a checkboxlist

I can see how to disable (or style) one option from a select list from this thread.

But i can't see how to disable (or style, or add a class) to one particular checkbox within a checkbox list.

I can make the label of just one checkbox in a list and style that:

	$form->addCheckboxList($a_field, $label);
	$c = $form ->getComponent ($a_field);

	$el=\Nette\Utils\Html::el('span')->setHtml($option['label']);
	$el->style['color'] = 'green';
	$arr[$option['value']] = $el;
	//...
	$c->setItems($arr);

and i add a class to all the checkboxes in checkboxlist:

	$c->getControlPrototype()->setAttribute('class', 'my-class-for-all');

but not just one of the checkbox inputs. getComponent() does not work on the individual checkboxes in the list.
any idea how I can grab/style/add attributes to just one?
i can't even see how to set the defaults of a checkboxlist

thanks