go to ebay put in kitchen timer ! £3
simple and does the job.
clip ones will clip on your knee board
Magnetic ones will stick to a metal yoke
digits are usually big
buttons are often big and simple to use
also put some Velcro on the back, seems to be a theme with GA cockpits and Velcro lol
I found all that was really important was leg time, rate one turn times and FAF to MAP etc, also the LED ones show up easy in low light. If you get one with time on then useful to set it to zulu
Ian