Ordered something overseas that came with a US adapter, planned to replace it with an NZ equivalent but I can't find one on Trademe or on the usual stores I check. There are adapters very similar to with slightly different input or output, but I know nothing about how interchangeable power adapters are, so I need some help.

I'm trying to replace a power adapter that has the following on it:

AC Adapter

Input 100-240v~50/60hz 0.2A

Output 5v === 1a.

The head of the adapter is silver with a black tip on the end and two little metal bits inside the tip. It measures something like 5mm outside, 2mm inside the tip.

It is to power a tiny optical switch box.