as has already been posted a mechanical lock may be your best solution but
if you really need electrical locking you will have to get power to the
Most access systems are 12-24v powered and come in 2 parts.
1:- the reader
2:- the locking mechanism.
The reader can be a keypad,swipe card,fob or even a radio receiver whilst
the lock can be a heavy duty magnet,shoot bolt,mortise keep or Yale type
These are but the most common and hundreds of combinations are available.
Try a search of BPT , URMET , BSTL , VIDEX websites and browse their Access
Control pages for ideas prices etc.