StarTech.com 10' RS232 Serial Null Modem Cable - 10ft Null Modem Cable - SCNM9FF - Serial Cables - CDW.com
76000264 Digi | Cable Assemblies | DigiKey
Crossover or "Null Modem" vs. Straight Through Serial Cable - Decisive Tactics, Inc.
Serial Port and Modem Cables
What is an RS-232 crossover cable? - Quora
Amazon.com: Letotech Cross Wired USB Serial Cable DB9 CP2102 ZT232 USB RS232 to DB9 Null Modem Cable PC Control TV Cable (Null Modem Pinout) : Electronics
USB RS232 DB9 Female Crossover Null Modem FTDI NMC Cable for TV RS232 Service Port STB Config Scale Console - AliExpress
RS-232 Connections That Work
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