Если менять, то с учетом будущих измений
/classes/Product.php
public function getAnchor($id_product_attribute, $with_id = false)
{
$attributes = Product::getAttributesParams($this->id, $id_product_attribute);
$anchor = '#';
$sep = Configuration::get('PS_ATTRIBUTE_ANCHOR_SEPARATOR');
foreach ($attributes as &$a)
{
foreach ($a as &$b)
$b = str_replace($sep, '_', Tools::link_rewrite($b));
$anchor .= '/'.($with_id && isset($a['id_attribute']) && $a['id_attribute']? (int)$a['id_attribute'].$sep : '').$a['group'].$sep.$a['name'];
}
return $anchor;
}