EBay would have given you a window for delivery, based on the seller's method of shipment and his handling time.
If the last date of the window has passed, go to the Resolution Centre at the bottom of this page and open an Item Not Recieved Dispute.
The first suggestion is that you Contact the Seller.
Do NOT get into a conversation. All you want from him is a tracking number.
Do NOT accept an offer of a replacement.
Do NOT close the dispute until you have either your money back or the item.
Shipping from Europe is usually quite fast, 20 days or less by Air Mail.
If you are very worried, you can open a Dispute with Paypal.
The Paypal Resolution Center is under Tools on most PP pages.
You can open a Dispute at any time after payment.
If the seller cannot prove delivery (not shipping, delivery) you will be refunded.