Well, a small sun dial (made in Switzerland, maybe by Breitling, or Rolex)...
Paired with a compass, and a variation chart in my wallet.
Solar power... rather economical, no batteries or winding required.
Will send it back on warranty, does not seem to work very well at night.
xxx
Happy contrails
P.S. Dont forget to add a leap second to UTC this next 01 JAN...