You either need a new cylinder with key
JA-JLM477 - Lock & Key
Or you can have a locksmith repin the cylinder you have to work with a key.
I think option a is the cheaper alternative. It's Part # JLM477
Oh, scratch that, I see that the part is not in stock.
You can remove the cylinder and have a locksmith key it any way you like... you will need the proper blanks though. Perhaps you can find someone selling their old keys. A locksmith can re pin the cylinder to existing keys too.