The 4LED 2AA gives a fairly good output (almost as bright as an Innova X5t. The head is removable.
The LEDs are not matched particularly well and they are run in parallel. This allows some individual LEDs to be a little dimmer than others.
I find that on mine, I can unscrew the head a little (1/4 turn) and have only one, two or three LEDs light up. I did not bother to measure the current to see if that would give longer run-time.
Around here you can buy them at Orchard Supply, a Sears subsidiary. About $16 US.
Daniel