Wired computer mice might seem archaic, but they're incredibly easy to use. It is not a particularly advanced model, with no more than three buttons.
Speedlink KAPPA Mouse - 3 Buttons - Optical Sensor, Black, KAPPA USB, SL-610011-BK
Conrad Electronic
SpeedLink KAPPA Ergonomic mouse USB Optical Black 3 Buttons 1000 dpi Ergonomic