Makerfabs ESP8266 WiFi Shield (recommended) — DCC-EX Model Railroading documentation
ESP-12E ESP8266 UART WIFI Wireless Shield for Arduino UNO R3 | eBay
Keyestudio ESP8266 WI-FI Module Shield +1M Micro USB Cable For Arduino (Chip is CP2102-GMR)
Esp8266 Esp-12 Esp-12e Uart Wifi Wireless Shield Development Board For Arduino Mega R3 Module Mega 3.3v 5v Ttl Interface One - Integrated Circuits - AliExpress