USB-to-UART CP2104-MINIEK (mini evaluation kit) available for $5 – Dangerous Prototypes
CentIoT CP2104 Serial Converter USB 2.0 To TTL UART 6PIN Module
CP2104 USB to UART Converter Arduino Programmer | Makerfabs
TECNOIOT CP2104 USB to RS232 TTL UART 6PIN Connector Module Serial Converter Serial Converter CP2104 USB to RS232-TTL-UART 6PIN Connector Module: Amazon.de: Computer & Accessories