Based on a vintage Hollywood Cigarette Ring found by Mitch O'Connell: http://boingboing.net/2012/03/23/introducing-the-hollywood-ciga.html I have included a short and tall post version (Use the tall post so your fingers don't smell like an ashtray!)

Update:added a second file with a gap so it fits any finger size.

Customize the files for your own finger size over at Tinkercad: https://tinkercad.com/things/5kknrmVFVOo