You can try sending an email to Tim Cook!I bought my rMBP in the USA, but since I live in Greece the local Apple service are not authorized to provide a replacement. They tried to reseat the bottom cover and tighten the screws but still the left side creaks when pressed. They offered me the option to replace the whole casing including the battery (as part of a warranty repair) but I am not comfortable with such an 'operation' on a brand new computer. It's an issue I can live with and I almost forgot about it, until I read your post...
I live in Romania and a friend had the same problem! After he writes to Tim got a replacement right away!