Laser emitter for serial communications?
First, just to pick nits, an LED is not a laser, and vice-versa.

That said, you might try eBay, searching for "laser module TTL", and you can get quite powerful lasers which can be digitally modulated, usually  in excess of 10 kHz - that's why you need to specify TTL. Beware of the small cylindrical units - they typically cannot run for more than 60 seconds without overheating unless you provide extra heatsinking. And the bigger ones will have problems with eye safety, but you can get around that by defocussing them. However, you really need to start learning about the ins and outs of eye safety, since more or less by definition you're going to be pointing lasers at people's eyes. Nowadays folks tend to really freak out if they find themselves looking down the beam of a laser (the wussies).

While you're on eBay, consider finding very narrowband optical filters at the wavelength you're planning to use. When you're operating in the great outdoors, Mr. Sun is not your friend.

Putting a detector in an old headlight is a decent idea in principle, but the details of actually making a robust mount will be more of a challenge than you think. Plus, the better your system gets at concentrating your incoming light, the narrower its field of view and the more difficult aiming it gets. Maintaining alignment also gets iffier, too. 

As an aiming guide, you might consider sending a constant stream of null data, as close to alternating ones and zeros as you can, and producing an audio output from the receiver. This will let you aim your system by listening to the tone, and such fast audio feedback will be enormously useful.

I'm not bringing this up to discourage you, just to let you know that you're in for a tussle.