The extremely popular single-board computer, the Raspberry Pi, now has a set of official peripherals. Specifically, the Raspberry Pi Foundation has released a wired keyboard and mouse, which come in two colours. The peripherals can be bought as a combo for £22 (~ US$29) or £16 (~ US$21) and £7 (~ US$9) respectively from third-party resellers.
https://www.notebookcheck.net/Raspberry-Pi-Official-keyboard-and-mouse-are-now-available.415653.0.html
I've long since went to a Lenovo Thinkpad keyboard (USB). Compact KB size, decent keys (for the thickness), and built in trackpoint (mouse). Compact in every necessary way that I use it. Uses a microUSB cable, as was common at the time it was introduced. Also uses a slightly older Thinkpad chiclet layout (fn keys are not grouped).