[y33t]

If you want a native options on a mobile device, Free42 and 48sx work great on Android (I believe at least Free42 is on iOS). Emu48 works on desktop (personally I like `dc`). Look at SwissMicros if you want a physical calculator.

[criddell]

If you want a truly native option, a small run of HP-15C calculators was manufactured a year or two ago and you can still get them:

https://hpcalcs.com/product/hp-15c-collectors-edition/

I bought one and am happy every time I use it, which is quite often.

[y33t]

Thanks for the heads up! Just ordered one.