Get an old siphon fill it with N2O, that is used in whipping cream. These small cream chargers are the same size as Co2 chargers ordinarily used in these siphons for drinking purposes. Be sure to leave out any trace of moisture! Now whenever you open a bottle, pour as you would normally, then after the session, just put the spigot inside the bottle and carefully expel the dry gas inside the bottle, expelling the oxygen in the process.
I was considering Co2 gas, but decided that could alter pH, which N2O apparently will not. I understand N2O is also known as laughing gas, so be careful, at least until the film is developed!