I wrecked the head on a Mini-mag recently, to the point that I could not get the front ring off to replace the lense. 
Then, I was doing a paste-up for photocopying using an Elmer's Glue Stick.  Eureka!  The orange cap on the glue stick screws right onto the end of the Mini-mag barrel, and you have a perfectly good water tight capsule.
It's a small thing.  Just thought I would share.