I might start with something smaller than what most folks here would call a "full size" searchlight, and see if it fits the bill. Something like the Acebeam L16 is pretty useful over 100 yards, has a dead simple interface (tail switch is momentary turbo, always turbo, no other functions; the side switch is click for on, hold to cycle through firefly/low/med/high, click for off), and is USB rechargeable. The numbers to key on for long-distance searching are "throw" and "intensity" (expressed in ft/m, and candela/cd, respectively; they are directly correlated). The L16 is 90,800 cd, equivalent to throw of 603m.
A step up in size and throw, but still easy to charge in your car and easy to use, is something like the Olight M3XS UT Javelot. Dead-simple usage: click on, click off, hold down to cycle modes. Throw 1000m, 250,000 cd.
The ultimate step up, which will require an account in another forum and waiting on a wait-list for an unknown amount of time, and will most likely require a shoulder strap or a custom handle, is the BLF giga thrower, well over 1,000,000cd. Even though it is probably not practical for your use, the video is fun to watch:
http://www.candlepowerforums.com/vb...-aspherical)&p=5136752&viewfull=1#post5136752.
Good luck!