Must be a good hardware store if they have that in metric. Most don't. I am not familiar with Cycle Resource, but converting to allen's is cool. I have bought some from the dealer where I used to work.
Soapbox time. Please tell me you are doing the sprockets as well. Chain and sprockets wear at the same rate. If you do one without the other, it will wear the new part in a fraction of the normal wear time.