Bought one of these a while ago for the pillar drill to ease the issue of lining up centre punched dots. Powered by 3 AAA cells It just about did the job, but it was never really bright enough and eats batteries. Low self discharge Nickel Metal Hydride rechargeables make it cheaper to run but are a lower terminal voltage and so less bright.
The batteries are held in a plastic carrier like this

I've got a very similar Ebay special LED torch that has an option of the same arrangement of three AAA's but can also take a Lithium 18650 cell instead
Tried an 18650 in the Arc Euro lamp and despite the peak volts dropping from around 4.5v to around 4.2v it works much better and for much longer (AAA's are woefully poor in mAh capacity in both alkaline and rechargeable variants) The 18650's are at least 3x higher capacity.
The 18650 will work as a 1:1 replacement but would ideally have an insulated sleeve around 19mm ID and 22mm OD to centre the cell in the battery compartment.
