Place two circular Polaroids on the overhead in the regular manner and set for extinction.  Insert the third sheet between these two and show that now some light will pass.

See the "Bauman" and "Rossing and Chiaverina" references below for the Quantum Mechanical explanation of why the insertion of a third polarizer BETWEEN two crossed Polarizers allows light to pass.

The Quantum Kaleidoscope units are hand held versions of the 3 Polaroid demo.  These also come with an activity sheet of activities.

There are also a variety of other demos and resources that are used for Quantum Uncertainty Principle.  They are:

#1 - (According to Gemini AI) - Variable single slit diffraction.  Explanation:

• The Setup: Shine a laser pointer through a very narrow vertical variable slit.
• The Action: Slowly make the slit narrower.
• The Result: Intuitively, you’d expect the dot on the wall to get smaller. Instead, once the slit gets thin enough, the light starts spreading out horizontally.
• The Why: Due to Heisenberg's Uncertainty Principle (ΔyΔpy≥ℏ2\Delta y \Delta p_y \ge \frac{\hbar}{2}ΔyΔpy​≥2ℏ​), a decrease in Δy\Delta yΔy necessitates an increase in Δpy\Delta p_yΔpy​. This means the particle acquires a range of possible momenta in the y-direction.  By narrowing the slit, you are "squeezing" the photon's position (smaller Delta y). To satisfy the uncertainty principle, the momentum (larger Delta p_y) must increase. This extra momentum manifests as the light "kicking" out to the sides, creating a wide diffraction pattern.

Mechanical Universe Series Episode 50: Particles And Waves - The Mechanical Universe.  https://www.youtube.com/watch?v=STJbtg-p4EA&list=PL8_xPU5epJddRABXqJ5h5G0dk-XGtA5cZ&index=50 

Mechanical Universe Series   Episode 51: Atoms To Quarks - The Mechanical Universe.  https://www.youtube.com/watch?v=6IWhRffFRc8&list=PL8_xPU5epJddRABXqJ5h5G0dk-XGtA5cZ&index=51 

Mechanical Universe Series   Episode 52: The Quantum Mechanical Universe - The Mechanical Universe.  https://www.youtube.com/watch?v=Tl-C1r3IabY&list=PL8_xPU5epJddRABXqJ5h5G0dk-XGtA5cZ&indexPhet quantum Tunneling and Wave Packet. 

Uncertainty Principle https://sciencedemonstrations.fas.harvard.edu/presentations/uncertainty-principle

An example of "you can't make a measurement without changing the sample" is to take a beaker of colored water.  When you insert a ruler to measure how high the water is in the beaker, the water level rises.