Considering the situation you are in is a no win situation I would try something a little different. Basically, we know the seller either intentionally or un-intentionally attempted to rip you off. You did the right thing by opening a PP dispute but now are left still losing money over someone else mistake.
Write the seller one last time to the email addresses you have for them. Inform them that even though you have won the dispute that you will still be out the money and item. Tell them that if they don't issue a refund within 24 hours that you will call your credit card company to file a chargeback. Tell them if you have to eat shipping cost to return their item, they will be eating a chargeback fee of $30 and ask them to check PayPal's ToS if they would like. Ask them why they would attempt to scam you and why they would want to be out $30 when you gave them every chance to do the right thing. It may work, or it may not work but at this point you have nothing to lose.
May not be the best advice, but it could work in your favor.
BK
