This is how i built my Boba Fett Starwars Blaster for my Halloween costume. I wish i had better documented building process but, it was not to hard.
Step 1: The Blaster
I used a Rebel Alliance Nerf Blaster i bought at wal-mart for $20 bucks. It was blue and orange. I took out all the screws holding it together and tore out all the guts and the barrel. Then I drilled holes just large enough for led lites to be passed through the holes. The leds came from a necklace a found at the local party supply store for $3. Note: the pet laser attached to the blaster.