HELP building a two heads laser

Hi, a friend want something like this for his violin;

LazerDiva - YouTube

I have experience building leds flashlights but I dont have experience in Lasers, so, I need help with, how to drive them, I am thinking in use some 18650 bateries, maybe two or three in paralell, heatsink the lasers, do I need lens? Head laser, no more than 5mw green lasers and the most important, where to buy all the staff...

Thanks all...

My recommendation: Use laser Modules, not "from scratch" parts, for your first build. So you know though, to make a module you need to know the Vf and If (forward current and voltage) of the diode, and match a driver to it, and find a housing that will heatsink the diode precisely and accept a standard lens.

A module will have the apropriate lens, housing, diode, and driver all connected and set up properly, you just add battery. Mohrenburg has some super inexpensive mini 5mW red modules for sale for like 50cents each.

A 5mW green module might be harder to find, but that is because most people who buy green modules buy very powerful ones. You cannot build a green laser from parts like you would other colors (unless you spend $250+ on the diode alone, with a waiting list!) as they use a method called DPSS, it's an IR diode with precision aligned crystals. An alternative is finding a cheap green pointer (beware, often they are marked as 5mW but are up to 100mW!) and gutting it carefully, and using the guts.

Thanks for the info, what about this head?

Geniune New Wish 5mW Green Laser Module (5V) - Worldwide Free Shipping - DealExtreme

Can you point me to where to find what I need?

I forget, what about to buy a pair of laser pen and use the parts?