A really simple project for my elementary school STEAM club. Takes a minute, no tools.
Step 1: Everything You Need
A 2032 battery (50 for $7.50 - Aliexpress.com)
A super bright (and directional) LED (500 for $5.99 - Aliexpress.com)
4" electrical tape (any store, anywhere)
A 1" x 1" piece of foam sheet (32 sheets - guess how much-The Dollar Tree - makes hundreds)
Step 2: Two Seconds to Make
Cut out a 1" square of foam. Cut out a rectangle about 1/8" by 3/8". not critical how big, just leave a slot for an anode). Put the battery on foam, negative away from foam. Slide LED over foam and battery. Cathode touching Neg side of battery and anode over slot in foam. Wrap tape around. The tape is on the battery and around the foam, so nothing tries to move. It does not need to be tight enough to bend foam. I found wrapping super tight does no woek at all, as the foam cannot compress.
Step 3: Ta-da!
Squeeze with thumb on foam side. The light is bright and very directional. (It shines like a spotlight, don't use diffused LED.)