I actually made this over a year ago, but had most of the materials necessary to re-create the steps.
1 bandana from the craft store (or make your own, but that’s another I’ble), $1.50
1 battery powered Christmas-lights novelty necklace, ~ $7
thread to match the bandana
masking tape – optional
Link to YouTube video:
Notes: This is not washable. In order to have a washable bandana, you could sew the lights to a strip of cloth and use Velcro to fasten the cloth to the bandana. I just have my dog wear something washable if he is likely to get muddy.