This thread serves as reminder to all of us, what can possibly go wrong while importing electronics items. And how important is it to use a good courier service *with tracking* ability. EMS/Unregistered parcels are only good for low value items.
OP, you can two things:
a) Opening a Dispute with Paypal, if its not more 60days since payment(probability of success: 30%)
b) Following up with custom office((probability of success: 1%)
I am not saying these would work, but there is no hard in trying. I can understand why you are mad at mp4nation but they it looks like they are not at fault. Next time, use a better shipping method and get the package insured if possible. it sure would cost you more but there is a surely that you will get the package.