You pay the price, buddy. Spend the output that is yours and put a high fee, which as said above, is called CPFP (Child Pays For Parent). There is no other way if you're in hurry. We all want our transactions confirmed the soonest possible, but some of us want it more than others. 

But, you do fully trust the sender, unless the sender won't take their goods in return until the transaction confirms.

Also, why telling the sender to make another transaction and just not broadcast the same?