Amazon.com: StarTech.com 1m Black DB9 RS232 Serial Null Modem Cable F/F - DB9 Female to Female - 9 pin RS232 Null Modem Cable - 1 meter, Black : Electronics
Delock Products 86604 Delock Serial Cable RS-232 D-Sub9 female to female null modem with narrow plug housing 10 m
The RS232 Standard
Amazon.com: DTech RS232 Cable 15ft Null Modem DB9 to DB9 Serial Cable Male to Male RS-232 Cord Cross TX RX line for Data Communication (15 Feet, Black) : Electronics