Watch with alarm or travel clock

Modern travel alarm clocks can be tiny - no bigger than a cassette tape. A moderately priced digital watch with an alarm and dual time (for timing those phone calls home) will also work if the alarm will wake you reliably - the sound is often not loud enough to stir a deep sleeper. You will have some early trains to catch, and buying a loud, reliable alarm clock is probably going to be money well spent. Make sure you have a spare battery so that the clock doesn’t die on you at the worst possible time.