Portable LED Power Supply & Driver
Because you do not care about efficiency a single constant voltage supply with resistors will work fine. But current limiting resistors are inefficient and the brightness will diminish as the battery discharges.  The AL5809  CCR will provide "a good quality of light"

Battery operated projects should NOT use current limiting resistors.  A CCR like your AL5809 will keep the current constant over a wide range of voltages (e.g. 3-6V) 

For $15, 2 Panasonic 3350mAh 18650 NCR18650B Li-ion Battery may do better than a no-name Li-po battery pack. 

Other possible CCRsOn-Semi NSI50150ADT4G Adjustable Constant Current Regulator &amp; LED Driver 
or the  Microchip MIC4801





LEDs

The smallest would be Lumiled's Luxeon Color C Line

The most efficient (and small) would be the Cree XP-G3

The most efficient Color LEDs are OSRAM Olson SSL