LOL I loved the description of the film canisters recycled for humidifiers!! I think they are fairly hard to come by nowadays probably.
Years ago, I used to fill a film canister with beans or rice and use them to teach vibrato. So when you hold the object in the palm of your hand, you can listen to the sound as you make the vibrato motion back and forth. It also encourages a nice wrist vibrato, which allows for a variety of options in speed and intensity.
There’s another item that could replace the now difficult to attain film canister for both purposes. Prescription vials! I recently got a couple really long ones for some huge vitamin pills I had to take. Ive been trying to think of ways to recycle them.