Inexpensive end pilots watch with a stopwatch.
Worked for PPL, TPS, 1000ish hours, and CPL training.
To be honest, any half decent wristwatch with a stopwatch will be fine so long as you can read both at once. My personal foible is that I fit an "Animal" velcro watchstrap to my watch - which I use to strap it around the yoke (or something convenient in front of me if the aeroplane has a stick).
If on a budget, try
Argos!
G