If you have any 
non-punched XL cartomizers (45 mm carto body) you can use one of those to plug the tank so it won't leak. 
Being a bit longer than a standard cartomizer, it will stick out and seal both ends. 
Punched XL carto probably will not work, unless the hole is low enough on the carto body to remain outside the tank.
An XL cartomizer also works well as make-shift carto removal tool, if you need one in a pinch. 
You can use a file to take any edge off of the bottom where the atty connector is joined, if needed.
And if you have the right size of O-ring, you can even put one around the atty connector to work as temporary seal (like at the bottom of the tool in that picture).
Never underestimate the ability of a Submariner to improvise.