Can you use Shimano 11 speed chain pins on a 10 speed chain?
My understanding is that the chain pins for Shimano 10-speed chains are 6.0mm in length and the pins for the 11-speed chains are 5.8mm in length. That is pretty close, but I wouldn't chance it. I also don't know for sure if the pin diameter is the same and I don't have an 11-speed pin to measure. 

A simple google search turns up many places where you can purchase the 10-speed pins. Even better - I have to believe that nearly every local bike shop in your area would carry 10-speed compatible pins.