Allow 30 days to pass from order, then contact the seller of the item you have NOT received. It may turn out to be the same person (even if there is a different business name).
If the seller is in China, it would be very expensive to return the item you did get. This is entirely the seller's error and while you may want to be helpful, there is no reason for you to be out money.
(Within North America, it can be possible for these mixups to be straightened out fairly cheaply by forwarding.)
Don't concern yourself too much about the incorrect parcel you did get. If you don't have a satisfactory resolution by Day 43 after purchase, file an Item Not Recieved dispute with Paypal /eBay.
A replacement may be satisfactory if the seller is shipping from North America, but from overseas, ONLY accept a refund.