retrocomputing

Some of the best keyboards ever made, many of them beige, use a 5-pin AT connector. These can be trivially converted to a PS/2 (not P/S2) port with a small adapter.

You might want to browse some mechanical or vintage keyboard forums to see specific models that other people use.

https://deskthority.net/

https://geekhack.org/

You can find native PS/2 mice (like the Logitech First Mouse) on auction sites, sometimes even in new condition. I have also seen adapters for plugging USB mice into PS/2 ports, although I don't know if they work with every model.