You are covered by the eBay Money Back Guarantee.
Since the seller is being obtuse, open a Not As Described claim.
Even if the seller has a No Returns policy, they still make Refunds.
Whether they like it or not.
The seller does have the right to demand the return of the plates (even with a No Returns policy) but he must send you Return Shipping.
Some sellers panic at this point, since they don't know how to send a Canada Post shipping label.
This will give them an idea if they just want to send money to cover your cost for return.
https://www.canadapost-postescanada.ca/cpc/en/tools/find-a-rate.page
Or.
They can ask eBay to step in and send the label for them.
Or
They can buy Canada Post labels on Shippo .com from the USA and possibly other sites, like Pirateship.
You can find a link to the MBG and claims on your original invoice.
Come back if you have problems.