Hi Daeng,
if you are using the normal type 9V battery like this
http://en.wikipedia.org/wiki/Nine-volt_ ... t_0849.jpgit is not suitable, its for small current application. for this application which use Servo motors it will drop the voltage very fast.
one servo can take up to 1A of current which this kind of 9V battery cant afford to give.
the battery used in the project at instructable is 3 pcs of Li ion battery which give around 11.1V norminal voltage.
u can use 5 to 6 PCs of AA size battery or NiMh battery to get 6V to 9V battery with enought current capability.
if u have 9V or 12V Ac DC adaptor around which can support at least 1A, then you can try with it. i think u can try find electrical appliance that use ac dc adaptor, see the label if it meets the requirement.