This illuminated ring for Halloween uses a 2032 battery and a white LED. A real pumpkin was scanned, then the mouth, eyes and battery slot were inserted using Tinkercad.com.
Using a 3D printer (or service like 3dhubs.com) print the ring, face upward.
Tape the LED to a 2032 battery. The long leg on the LED goes to + on the battery.
Insert the battery/LED combination into the slot on the back of the ring. This should last for a few days--then it will require a new battery.