I've got a lot of these black corks hanging around from bottles of Apothic wine that somehow got emptied. I am always needing floating keychains as I'm on the lake a lot so I whipped up a way to recycle these corks. 

I printed these oriented as shown in the screencap from my slicer. I used a 20mm long M3 to fasten the two halves. It's meant to have a gap between the halves so it can accommodate multiple cork sizes. 

Update: I added a V2 which is a little thicker around the hole for the chain.