I sure wish they had those contraptions when my kids were young. Back when my two boys were still young and reaching that age of temptation, I had to be a bit more inventive.
After some intensive prayer one night, the LORD gave to me a recipe for a special salve to place on the child's hands before bed:
1 Jar of Vaseline
1 Bottle of Tabasco sauce
2-3 drops of red food coloring
1-2 leaves poison ivy, or 2-10 drops of poison ivy oils (depending on desired strength)
Scoop the Vaseline into a more manageable container. Mix the other ingredients until well combined. Rub this into the child's hands before bed. Better yet, you could place it on their hands before bathing, since the Vaseline does not come off easily in the wash, thus preventing them from partaking in the devil's act while cleansing oneself. Be sure to wear gloves while applying to your child, since you're not the one needing instruction!
The special salve will keep them from masturbating because of the simulated hellfire that occurs if their special parts are touched. I placed this on my children's hands until marriage, and they are both very strong, successful children of the LORD. They also have very calloused, tough hands, perfect for toiling in the LORD'S beautiful cotton fields. Such beautiful hands...
I hope this helps someone out there. God bless!