I haven't made any or even thought it through, but why aren't the cones that use O-rings to close bottle stoppers turned from wood instead of steel? Wine and spirits are gentled and stored in wooden barrels and casks, so I would think cones turned from oak or hard maple with 3 grooves for 3 different O-rings might work. They could be attached to exotic wood tops or integral as a complete stopper.
Warping and size or out of round humidity effects might negate using wood since stoppers can end up in many different towns and fridges. Staining might be an esthetic concern also, although most stoppers are for show and not for blow. There may be other reasons that I failed to think of (not uncommon).
Wood seems to 'go' with wine better that steel, but I don't think Ruth Niles needs to lose any sleep over my wonderings. :)
Turn to Safety, Arch Fortiter