Thanks all for the help. I ended up finding a correctly sized cork at True Value Hardware & I just drilled an appropriately sized hole. Seems to be working fine.
Also, I confirmed: DO NOT USE THE BLACK PLUGS SOLD COMMONLY AT HARDWARE STORES. They contain sulfur.
Oh & there are three homebrew supply stores in my area. EVERY SINGLE ONE OF THEM IS CLOSED ON MONDAY. Which f-ing blows as it is my only regular day off.
So I've already started a brew this morning and I just realized I don't have another airlock bung (ie adapter/cork) I've been brewing for only a short time and this is the first time I was going to have two going at once (one, with the airlock & bung I have in my secondary; todays to the...