Bought a bunch of these from RadioShack. Pass them out to my friends with gold monsters. Don't know why the price went up. They were on closeout last month for a buck-fifty each. Now a little bit more. But they work with my Grey Ghost, Sun Rays or any other headphone. Nice tight fit works well.
https://www.radioshack.com/products/stereo-inline-adapter-1-4-jack-to-1-8-stereo-plug