The Petzl Core can be easily fitted in between the two parts of the Tikka2 (see movie below for instructions on how to do it exactly without damaging your Tikka2).
It is fitted with a mini-USB socket through which it can be recharged in about 3 hours and should last about 300 recharging cycles.
By installing the Core OS software from Petzl and connecting the headlamp via this USB connection to a computer you can modify the three preset levels for any activity. Just move one of the bars (intensity or duration) into the desired direction.
With a weight of 31g the Core beats three traditional NiMH AAA-type batteries (37g).
The Core is (splash)water proof (ipx4).
European retail price is about 29.50 Euro.