The best Topo maps for that area are almost certainly the LINZ Topo50 series.
These are freely viewable online. I use this and other maps on my phones, tablets and notebooks using OziExplorer. Unfortunately some conversion is necessary and there is is cost involved for the software.
I also use several other paid apps that can view the same Topo50 mapset.
For Android devices some free versions of apps will allow viewing offline with a little effort. Back Country Navigator etc. come to mind. A search in the Playstore for "NZ Topo50" will find a couple of apps. Untested.
Here is the definition available. Low resolution screenshot from OziExplorer on my Android tablet.
If you can pinpoint the location a little closer I could post another screenshot.
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