This is an enclosure that houses a D1 Mini style microcontroller and a 30mm Sanwa-style arcade button.

You can then use ESPHome to create and flash the firmware for the microcontroller. I've included a sample YAML configuration file below. Make sure to add your MQTT broker and WiFi information.

esphome:
  name: arcadebutton
esp8266:
board: d1_mini
Enable logging
logger:
ota:
password: ""
wifi:
ssid: "YOUR SSID"
password: "YOUR PASSWORD"
Enable fallback hotspot (captive portal) in case wifi connection fails
ap:
ssid: "arcadebuttonfallback"
password: "asdf1234"
captive_portal:
mqtt:
broker: "YOUR MQTT BROKER"
binary_sensor:

platform: gpio
pin:
number: D4
inverted: true
mode:
input: true
pullup: true
name: "button"

Simply solder a pin header between D4 and GND to connect your button inbetween. I used these cheap little wire harnesses that come with plugs that i got with an arcade controller kit.I used cheap little wire harnesses that come with plugs.

The mounting bracket is a bit loose. Add some spongey stuff to the flat side and it'll be good. I may try to design a better version later, but it works for now.