Penguin Sprayer takes a bullet

[FloorCareMD]

Try one of those "winter closing" plugs from an above ground pool supply place if hole is not too large.
http://www.amazon.com/WINTERIZING-EXPANS...B00404O5RG

Here is a 2"
http://www.ebay.com/itm/NEW-2-Rubber-Exp...0657552995

I am sure if you look for the right size, you will find one.
May have to drill out a round hole first like Hoss suggested.