These are the best places to start on Twain in Australia and New Zealand:
Miriam J. Shillingsburg, _At Home Abroad: Mark Twain in Australasia_
(Jackson: Univ. Press of Mississippi, 1988).
Miriam J. Shillingsburg, "Down Under Day by Day with Mark Twain," _Mark
Twain Journal_ 33:2 (Fall 1995), entire issue. Page 39 contains a
of Works by and about Mark Twain Down Under."