if it's gonna take forever to get one, you could make one to get you going.
find a large bolt with the same thread, cut the head off, drill a hole in it and tap it. you can use an adjuster off an old caliper brake, or buy one from a bike store for a buck.
you wouldn't even have to tap the threads, you could just drill it so the adjuster slips in, and adjust it by tightening the cable, or at the clutch lever.
or, you could do my brake noodle mod.