Has a TON of information and very good substantial reviews of a large variety of regular flashlights, LED lights and LED conversion bulbs – The guy gives you runtimes, beam patterns, lumen ratings and all kinds of other info.
A 3 Watt Maglite LED will illuminate to 50 Yards no problem and are pretty cheap and you can get pressure switches for them.
You’ll want an LED that uses a single named LED to get to 100m – Either a Luxeon or a Cree, you dont want one of the clusters of small LED’s (5mm Nichia’s usually) as they are very good long running lights, but dont have the throw of a single Luxeon or Cree.
Look for a reflector (silver bit) that appears to be like orange peel with a mottled surface, that gives a nicer smoother beam without any nasty artificats, but it isnt that big a problem with LED’s as it is with an incandescant bulb, but still something to look for.
Any of the 2 x CR123 battery lights that uses a Luxeon or Cree bulb should work for you. I’d try and find one with a Lumen rating of more than 65.
This is what I use –