Same Q everyone has due to the ridiculously poor user manual this comes with [single sheet of paper, folded into 1/3rds, w/ the same "how to unbox" text on both sides...] Anyway, I got a reply from the manf.; it takes a CR123a 3v lithium battery. This is great! I can now proceed to make an external battery box that takes regular rechargeables... ;-)
Good Q; I went to the importer's site just now to ask. If I get a response, I'll update this post. From the size of the battery compartment, it's something funky like a CR3 or other oddball camera battery. Once I know what it runs off of, I'll have to see if I can wire up an external battery box for it to run it off of something normal like AAs or AAAs... Like any Gen 1 NV device, it's bound to positively *EAT* batteries, so something else that is either inexpensive or rechargeable is an absolute requirement!