i'm answering my own question here. i had emailed harris and they got back to me right away. the wrench, made by great neck, is sold on amazon, so here's the link.
http://www.amazon.com/Great-Neck-958...0652721&sr=1-1

despite the one star review from some other reviewer, i had a great experience using this for the past four years. i think it's really well made and super small, which is nice for carrying in my bag or on tour.