Just get a TI-84 calculator: it runs this:

https://en.wikipedia.org/wiki/Zilog_eZ80

Here is the TLDR:

- 24 bit processor

- backward compatible with Z80

- resets into Z80 mode

- Z80 mode has 16 bit addresses and 8 bit registers that can be used as 16 bit pairs.

- ADL mode (address and data long mode) has 8 bit registers that can be used as 16 bit pairs or as 24 bit extended pairs.

- A 8 bit MBASE register controls which bank of address space is seen by Z80 mode.

- ADL mode has two banks of registers: main B, C, D, E, H, L and alternate B', C', D', E', H', L', with some support for fast switching between them.