That means you need a good handset with good battery backup,
If you see almost all high end hadnsets dont have battery backup for more than a day.
Few Handset like samsung epic got good battery backup, but its bulky with slide out keypad.
one handset I am using is HTC Ozone (win mo 6.5), which is not that bulky but have qwerty kaypad, good battery backup, (as it use 1500mAh battery for non touch phone with qwerty)
works on GSM and CDMA, BUT you may say its not rich looking (personal teats )