Where and how much is it to relace a broken key?

I have a master key with a special thing in the groove of the key. I took it to home depot and they said they cannot copy it because of that groove. And now the key has broken (snapped cleanly in half) and I really need it fixed. Where can I get it fixed and or copied? And how much will it cost? I live in plano texas if that helps in helping me choose a location for fixing my problem.