How much battery power for LED and how to make it flicker
That's a high quality LED (if genuine) - depending on volume then an Asian sourced semi-equivalent would be much cheaper.  

Battery life is very very dependant on operating current.
For a battery of adequate voltage across the operating time     


Operating life =  Battery_mAh_capacity / LED-mA.  


If you operate the LED at 700 mA then 


3 x AA Alkaline cells with a capacity of ABOUT 3000 mAh would ooerate the LED for about
time = battery_mAh/LED_mAh = 3000/700 = 4+ hours.  
A rechargeable 18650 LiIon cell of 3000 mAh would provide similar operating time. 


If "cheating" is acceptable, using an existing (low cost) low power flickering-candle-LED to drive your power LED, similar to this circuit by the great Dave Johnson, or a simple but elegantish version here. 

Alternatives could be a low cost microcontroller (from about 20 cents US)  - ATtiny85 example here and ATtiny13 version here or a counter IC connected to form a pseudo-random number generator. 

Many ideas here - Google image search on - candle flicker circuit