L. Paul Verhage KD4STH
One of my local Wal-Marts is selling a HD DVR dash cam for $9.
I need to look further into this but this camera can record 1080p HD and includes a 4GB SD card which you can increase to a larger memory. It does have night vision although I don't know how well that's going to work for night time use in near space.
It runs off of 12 volts so I suspect it will work with 3 lithium cells.
This may be an inexpensive and lightweight camera for BalloonSat use.