Micro chest lock - where to found hardware?

This is not a question about Arduino, but closely related to Arduino-driven project. I am planning to make automatically unlocked mini chest. It will have some kind of electrical lock which will be opened by Arduino signal. The question is - where to find simple and not expensive electrical driven lock mechanism with size not more then 10 x 10 mm?

What are HW bazaars you may suggest?

build one with a servo?

robtillaart: build one with a servo?

If it will stay locked when Arduino is powerless (spring?), it may be a solution. Did you encountered a servo which is little enough?

How big is the chest?

10 x 10 mm is small for a servo. - http://www.pololu.com/catalog/category/23

How about wiring a small electromagnet yourself with a small nail and a spring?

10 x 10 mm is small for a servo

My feeling that servo is overkill here. I do not need things to spin - I need it only tiny metal part to be pushed and pulled without additional mechanic, if it possible.

Reliable self-produced electromagnet with spring requires, at least, plastic frame for it.

Chest let say, as big as this one or a bit bigger.