http://www.x-eng.co.uk/

Anybody tried the handbrake thing ? Is it worth the $$

People are raving about them, theres some other folks just making their own, if you see much mud then they're supposed to be a major bonus as they don't fill up with muck.

any cable actuated caliper from a car with rear disks should be easily adapted to fit a simple steel disk bolted on instead of the drum,

see: http://www.hillbilly4x4.org/forum/index.php?a=topic&t=1077 as one example, he's using a rover 800 rear caliper, not something easily found stateside, but similar units should be availabe from a breakers, or if you want to go spendy, wilwood do a cable actuated caliper too