I've been looking for a small, light GPS that just tells you location and altitude.
This is what I found TripMate850:
- location/altitude/speed
- tiny (72 x 27 x 25 mm)
- 57.5 gram (with batteries)
- 12 hours on 2xAAA batteries
- trip logging

This plus a map (I always use map) is perfect

Does it show your location in UTM? If not... you're better off just not carrying it. It also only supports WGS84, it seems.