People are unlikely to make it for you. They've got their own stuff to code.
However, it looks pretty easy to do, and would be a good learning tool if you're going to learn to code. Just look up the sniper's code, and look into the 'draw beam' 'maintain beam' and 'destroy beam' function things, and weld them into your weapon.
Or you could use the code that draws the targeting dot for the RPG. That would be a more realistic laser sight than a visible beam. Probably wouldn't be too hard to attach that to other weapons.