I don’t have any more and want to start a third batch and I don’t feel like the long drive to the supply store (already have all my ingredients). Thoughts?
I use foil over the mouth of the carboy most of the time. Once active fermentation has stopped, sometimes I will put an airlock on it. Sometimes, I will just leave the foil on a few more days and then keg it.
I’d always try to use one, but in your situation I’d use a piece of sanitized tinfoil. The CO2 will push air out and the foil will keep nasties from falling in.
ziplock bag will also work. Might be a little easier as it is already “formed” to fit over the mout/neck. I’ve used this in a pinch.