electric or manual line lock?
the only reason i would use one is if you converted to rear discs and no longer have the stock ebrake. They basically keep pressure on the pads after your foot is taken off the brake pedal, theoretically giving you an ebrake. I would not suggest this as you main ebrake as the do fail and hit does happen.
Electric one operate as always closed till 12 volts is applied OR always open till 12 volts is applied. The first would allow you to use the line lock without draining your battery. The second would be set and drain your battery and then release the brakes...
Manual ones are basically a ball valve operated by you, depress the brake turn the valve and then release, result is a ebrake...kinda
As for who sells a kit
http://www.downeyoff-road.com/ChassisComponents/DiscBrakes.htmlbut it is overpriced and i am sure you could scrounge the parts together for cheaper