Not "we could not find any." We looked, and the shelf is empty. Here is the evidence, so you can decide whether that is an opportunity or a warning.
The central bank policy rate is 2.50% (Official Cash Rate (OCR)). source
NZD, empty. NZDD (Easy Crypto) and NZDS (Techemynt) both exist as 1:1 stablecoins with verified contracts on Ethereum and Polygon; neither pays yield, and the only 'earn' route is third-party DEX liquidity mining.
An empty shelf in a currency with a real policy rate is a gap between what savers are owed and what they can reach. It closes when someone with the licence to hold the underlying paper is willing to put a claim on it on-chain. Until then, holders of NZD choosing to earn are choosing to hold a different currency, whether they have priced that decision or not. The calculator prices it.
See every currency or read how we establish that something is absent.