All you need is a CD case, and you get a perfect circular aiming dot :)
Have fun making!

Step 1: Tools and Material

All you need is:

- small saw

- glue

- dremel tool (a hot nail can poke a hole in that too)

- old CD case (maybe 2)

- 3V button cell

- LED (blue LEDs run on 3V, so no other parts needed!)

- pair of pliers or something 90°angled to bend the main part, plus lighter

Step 2: Step by Step Video

THE STEPS:

1. Print and cut out the template (cardboard will work best, paper is too thin)

2. Place it on the clear CD cover, and grab a marker

3. Works best with a small saw: Cutting it out

4. Mark a stripe of 4cm in the center

5. Use a pair of pliers and a lighter to bend it by 90° on each side

6. Cut out 2 L-shaped edges (from another clear CD case lid)

7. Glue them onto the first part.

8. Make the 4 cm wide, 9 cm long centerplate (same clear plastic) and glue it on the L-pieces

9. Grab the black disc-holding part cut out a piece as shown in the video and glue it to the rear

10. Make 2 side plates, and glue them on

11. Glue in a tiny L-plate to make sure, the battery is held in place, same for the LED

12. Glue on a stripe of the clear stuff to cover the LED and battery

13. Time for paint, tape off the exit hole and rear section...then cover it in black, 2-3 layers.

14. Glue in the display and done :)