I seen a home made set-up on a truck in Tellico and spoke to the guy about it. He took the front rotor and caliper off a 650 knight Hawk and used a WillWood master cylinder. An E-brake handle was used from a junk yard Mustang II. It seemed to work really well and the cost was pretty cheap. He bored the rotor to fit over the output yoke and welded it on. Made a bracket from some 2" angle for the caliper that bolted to the transfer case and poof...e-brake!
Not real sure how much holding power this set-up would actually have but it was holding a full size Chevy truck on lower 2...smoked clutch.