weekend,
Actually you don't need a master link.
If you use your chain breaker correctly, you can put the chain back together.
Press one of the chain pins out just far enough to allow the links to separate. The pin will remain in the plate opposite the push direction of the tool.
Tip: When first pushing the pin out, it will be tight for about one turn. Then it will be easy for several turns. The handle will then get tight again as you attempt to push the pin completely out. You don't want to push it all the way out, so when the handle starts to get tight the second time...Stop! and check to see if the chain will come apart. If not, move the pin in small increments with the tool until the chain separates.
Get your chain sorted out, and then use the tool to push the pin back in. No master link, or trip to the store, needed.
Jim