FTDI FT231X USB to UART USB A TO DB9 Female RS232 Cross Wired Null Modem Cable for TV Box DVB STB|rs232 null modem cable|modem cablenull modem cable - AliExpress
What is the schematic of an RS232 Null-Modem? - Ferguson Wiki
White RS232 Null Modem Cable Female to Female DB9 5ft 1.5m Cross conne.acg | eBay