Simple Wifi RS232 Modem v2 from HAL's friends on Tindie
BB-9PMDS - Advantech - RS-232 MODEM DATA SPLITTER, 9PIN DTE-DCE
RS232 WiFi Wireless Modem for Vintage Computers from ArcaneByte on Tindie
StarTech.com USB to Serial Adapter - Null Modem - FTDI USB UART Chip - DB9 (9-pin) - USB to RS232 Adapter - Add a Null Modem RS232 serial port to your laptop
Industrial Multidrop Modem | TD-23 LV with relay ᐅ Westermo
Simple Wifi RS232 Modem v2 from HAL's friends on Tindie
ATC-871-S1 - RS-232 Mini Power 100mW Wireless Radio Modem. 500m communication distance, converter
TC1200 RS232 Fiber Optic Modem with Handshaking - TC Communications
DB9 F/F Serial RS232 Mini Gender Changer - Null Modem Adapter - Coolgear
TC1200 RS232 Fiber Optic Modem with Handshaking - TC Communications
RS-232 Modem Eliminator - DB9 Male/Female | Black Box
LINOVISION Rugged and Versatile Cellular Router & 4G DTU with RS232, Industrial 4G LTE WiFi Router with Dual SIM Cards Slot, Supports AT&T and T-Mobile | Linovision Global Store
Null Modem Serial DB9 Serial Cable (DB9), 10 ft. | Eaton