You are looking for a CPM1-CIF01 peripheral to RS232 interface. Another option is the CQM1-CIF02 peripheral to RS232 cable (no need for a serial cable.) Both items have sold in the last week for under $50 on ebay.
Thanks Jay for the info. I am anxious to get this thing connected.
I assumed when I bought it that all I would need was a serial cable.
The item you mentioned was probably on sale the same time I bought the PLC.