In the movie "Once Were Warriors" the gang members are wearing these
fantastic woven leather vests (and a couple of leather pants with
weaving).  They have embossed designs on them as well.  (The leather
weaving seems to be a take-off of grass weavings.)

I'm assuming these weren't "off the rack" but designed by someone
associated with the film.  Is that the case?  If it was designed, I
want to know who and get contact information.  I need specifics.

Costume Designer = Pauline Bowkett
http://us.imdb.com/name/nm0101185/

As someone who spent a lot of time in and around South Auckland, my
impression is that some clothing and all of the tattoos are very
stylized and not typical of the real world.