You might consider the Garmin Forerunner 201. It's light, wearable, lasts 15hrs on batteries, has slope and elevation tracking...
Here's a review...
http://www.tramsoft.ch/gps/garmin_forerunner201_en.html
The Gecko 301 also has nice elevation features...
http://www.tramsoft.ch/gps/garmin_geko301_en.html
Both of these units are fairly compact.