Yes, using a battery is possible, but not suggested. For one, the current draw is around 50mA so it’d be like using a battery on something like a Boss DD-7 delay pedal…you’d only get about 6 hours of use from one battery. Also, as you noticed, there isn’t a place in the pedal for a battery, so you’d have to use a “battery snap to barrel jack” adaptor…something like this:
http://www.voodoolab.com/shop/index.php?cPath=22_24_40