this is my first succesful (barely) attempt at electronics and soldering, so most likely if you make this it will be ten times better.

Step 1: Materials

for this you will need;

9 volt battery
1k resistor (brown black red)
2 leds
small switch

tools;

soldering iron
pliers
epoxy (i used hot glue)
metal saw

Step 2: Disassemble the Battery

Pry the metal lip back from the bottom of the battery and straighten the edges as much as possible with pliers. Carefully pull out the plastic base and save. After that the innards should slip out without much trouble. Cut the negative lead going down the side and save the connector. Save the case
(yes i did copy this step from YAN9VUSBC, after all it starts the same)

Step 3: The Leds

poke two holes in the bottom thing with a nail
stick the leds in the holes an hot glue them there
cross and solder the two positive led wires together and solder a wire to it
cross and solder the two negative led wires together and solder a wire to it

Step 4: Make the Circuit

solder the former negative 9 volt snap to the middle pin of the switch (not directly, with a wire)
solder the resister directly to a side pin on the switch (dosn't matter which)
solder the resistor the positive led wire
solder the negative led wire to the formerly positive snap

Step 5: Prepare the 9 Volt Case

I suppose you could sand the paint off (I didn't)
cut the case to about 3/4 in long (you will probably do better than me so you could cut it smaller)
make a rectangular hole in the side with a xacto knife

Step 6: Encase It

put the circuit into the case leds first
stick the switch in the hole
fill the case with hot glue, or epoxy
put the snaps in
While the epoxy or hot glue starts to harden, cut 1/8" slots at each corner to help them fold over. When the epoxy has pretty much set up bend each edge over to close the case. Burnish or sand any sharp edges.