Step 1: Materials
The LEDs were from an assortment I bought from American Science & Surplus - your basic 1.7V to 3V red, orange, green, white/clear LED.
The 100 & 200 ohm resistors were from Radio Shack.
The 25mm Beading Hoops were from a local bead store and cost $4 for 10.
The only critical component are the batteries, which need to have leads pre-soldered to them at the factory. The 3V lithium-ion batteries were from Mouser (Mouser part #658- BR2032-1GU,mfr part #BR2032-1GU @ $2.32 ea).
Step 2: Wrap the LED Leads Around the Beading Hoop
We'll start with the simplest case, a LED that doesn't need a resistor.
Use some needle nose pliers to hold the led & hoop in place while you wrap the leads. It'll be less strain on the LED.
Step 3: Solder and Cut Away Excess Leads
Careful you don't melt the LED. You could attach an alligator clip to each lead as you solder it to act as a heat sink. I learned this after melting a few LEDs.
Step 4: Prepare the Battery
Follow along in the photos...
1. Unmodified batteries.
2. Bend one lead over.
3. Flatten the other lead.
4. Bend one of the skinny leads down.
5. After bending one of the skinny leads.
6. Cut off the excess.
7. Bend the lead back up.
8. Ready for use.
Step 5: Solder the Hoop to the Battery
Figure out the which way lights up the led and bend a hook in the end you want to solder to the battery.
Solder it, trying not to heat up the battery.
Step 6: Make a Latch/switch and You're Done!
Bend another hook on the other arm of the hoop. Hook it in the bent lead of the battery to close the circuit and light up the led.
Step 7: Add a Resistor for Yellow and Red LEDs
Red & yellow LEDs draw too much power from a 3V battery and reduce battery life.
I used some 100 & 200 ohm resistors I had handy.
Wrap the resistor around one lead of the led, solder it, and snip off the excess.
I put the resistor on the lead that would later be soldered to the battery, thinking that would put less strain on it.
Step 8: Wrap the LED & Resistor Around the Hoop, Solder, and Snip Away Excess
Solder to the hoop just like with the LED without a resistor.
Then attach to the battery in the same way as before.