I'm looking for a low power 7 segment display. I need 4 digits. Any suggestions?
DigiKey.com has a bunch of 4-digit 7-segment LCD displays. Perhaps one of those would meet your requirements. I think they are raw displays so you might want to also look into driver chips.
The Nokia 5110 is cheap, low power, and doesn't require anything fancy. It can be configured as a 4x7, using standard digital clock software.