LEDs
From Rhythm Cons Wiki
Arcade LEDs are often sold by specialty stores. 5V LEDs with a 555 / T10 wedge mounting is the most common LED for DIY use.
This page will list stores by region.
North America
USA
https://www.cometpinball.com/products/2smd-bulbs
Europe
UK
https://www.arcadeworlduk.com/products/awuk-5v-10mm-wedge-base-led.html
France
https://www.smallcab.net/led-c-88_123.html
https://jammastar.com/gb/122-led
Asia
Japan
https://conn-lab.booth.pm/items/2411066
Korea
https://istmall.co.kr/us/goods/goods_view.php?goodsNo=1009992273 (Only 12V available - will be dimmer on 5V)