OK Boys, Wife thought of this one.
A hard rubber Hockey Puck fits the ID of the DD tube perfectly. Its tight enough to be rapped in with a rubber hammer, but it will probably have to have a hole drilled in it to pull it back out.
A brand new regulation Hockey Puck at you're favorite sporting goods store will run you 99 cents each.
Now the next thing is... Is there any reason not to seal up those salt scooper tubes???.
A2Jack