Does anyone know an easy/inexpensive way to "clone" an RFID card? (My work only lets me have one card, but I want to keep one in my car and one in a my wallet

Does anyone know an easy/inexpensive way to "clone" an RFID card? (My work only lets me have one card, but I want to keep one in my car and one in a my wallet since I need it both in the garage and in the building.) I figure it shouldn't be too hard, it's just sending out a radio frequency, right?