DB9 Male to Male NULL Modem Gender Changer RS232 to RS232 - PLCCable.com - Automation Supplies and PLC Tools
Amazon.com: DTech DB9 RS232 Serial Cable Male to Female Extension Null Modem Cord Cross TX RX line for Data Communication (10 Feet, Black) : Electronics
Building the Null Modem Cable
6ft (1.8m) DB9 F/F Serial RS232 Null Modem Cable - Black | Serial RS232 | Computer Cables | USB and PC
RS232 null modem pinout and wiring - DEV Community