Hi Tony,
I found this reference on Tapuhi, the database of unpublished manuscripts held by Alexander Turnbull Library in Wellington, New Zealand.
http://tapuhi.natlib.govt.nz/cgi-bin/spydus/MSG/ARCHIVESNR/MNRMENU.HTMRecord Title : Sheryn Sunderland - My family origins in New Zealand
Display Dates : 1990
Reference Number : MS-Papers-4280-083
Collection Record : New Zealand Society of Genealogists : 1990 Sesquicentennial Family Biography Competition collection (MS-Papers-4280)
Issue Restriction : Unrestricted
Collection Status : PART OF COLLECTION
Issue Status : Issuable ITEM
Quantity : 1 folder(s)
History : William Astle came to Auckland in 1842 in the St George with 91 other `Parkhurst' boys
Scope and Contents : The essay covers the period 1842-1940 and describes the lives of William and Mary Astle, Edwin Joseph Roden and Mary Astle, Gertrude Hannah Roden, John McCann and Annie Burke, Edward John McCann, Ida Irene Catherine McCann, Isabella Wishart Dickson, James Rose, Elizabeth Mary Rose, Alfred Edward Sunderland and Henry Edward Sunderland, all forbears of the writer.
Finding Aids : Published guide available
Names : Sunderland, Sheryn, fl 1990 (Contributor)
Astle family (Subject)
Roden family (Subject)
McCann family (Subject)
Dickson family (Subject)
Sunderland family (Subject)
Parkhurst Prison (Subject)
Subjects : Pioneer life - New Zealand - Auckland Region
Pioneer life - New Zealand - Otago Region
Institution : Alexander Turnbull Library, Wellington, New Zealand
I would suggest that other likely sources, since the Parkhurst Boys arrived in Auckland, would be Auckland Museum and the NZ Society of Genealogists
http://www.genealogy.org.nz/ You might also consider placing notices in the NZSG's nationally distributed journal,
The New Zealand Genealogist. The NZSG has a national membership of about 20,000.
Regards, riley