Brainstorm all you like! Let me know what you'd like to see in that box to punish or reward Lizzy!

A certain set of 3 alligator(no pun intended) clips with electrical stimulus inputs.

A ping-pong paddle to facilitate spankings would be an excellent starting point. It Could also create a scenario where someone could be doing "The Ping Pong Ball trick."

A flogger or similar implements could be discovered among the smuggler's effects in the containment chamber.