A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Andrew Nikitin
Date: 2016 Feb 12, 06:06 -0800
For a handheld device that is capable of storing timestamps at push of a button I used WP34s calculator. I used it in a context other than taking sights at sea, so I do not know if this will be applicable.
The calculator has an option of built-in realtime clock which you can access from a program and store a timestamp into a memory register.
The calculator iself is based off hp30b. It is and is much smaller than your typical "graphic" calculator and very light, you can probably fit it on the back of a sextant and operate with the same hand. The batteries last forever too.
On a con side, it is definitely not waterproof and there is no backlight.