yeah they make plugs for the bung or you can go to the hardware store and get a bolt or pipe plug that is the correct thread pitch. Most are 18mmx1.50. I also found one at a local auto parts store but when I returned again to buy another one they acted like they never heard of one lol. Online they are sold here http://www.o2bungs.com/
Also Google is your friend
. I just happened to no be busy. Good luck!