http://resolutioncenter.ebay.ca/
Normally the buyer pays the return shipping, although in some circumstances, eBay will require that the seller provide a return shipping label.
The reason for the 'buyer pays return' policy, is that not all buyers are honest and sometimes the buyer will demand the cost of shipping and then keep the item and the postage, or return something entirely different, or return as defective something that is exactly what was honoured.
Not too often, because most people are honest, but often enough that sellers are wary.
Discuss the possibility of a shipping label with your seller. This is however, impossible if he is not in Canada. The international postal system doesn't allow it.*
The Resolution Centre would refund your entire original payment, but not the return shipping.
The seller can, if he accepts that the problem was his error, refund your return shipping voluntarily, usually after he has his item back.
* Well, there is a thing called an International Reply Coupon, but it is very difficult to use, slow to arrive, and confuses the bejabbers out of most postal clerks.