Hmmm, I found mz old Garmin GPSmap! AFAIR it could do up to 28 Hours and had a transreflective display, and it could be used with OSM Maps. I think I might encounter a few situations soon where that is useful again.
@zem I use a GPSmap 62s for Geocaching. Works fine with OSM maps. You can always just carry a couple replacement batteries.
This is the social network for Conesphere.com's community.