Power source for four SG90 servos?

I'm trying to build a basic robot arm with 4 SG90 servos. I know better than to power them from the arduino, but I've got no clue what power source I'd need to provide enough current and voltage to power all of them while keeping them stable.

Here’s a site with some of the servo details:

Use 4 AAA batteries .
Have a look at the example with 2 servos and make a similar connection for 4 servos: RobotoId™ – House Robots Make Life Easier
Remember to connect the ground from the Arduino with the ground from the batteries.

4XAAA alkaline batteries will not provide enough current for even two servos, and it is very unlikely that 4xAA alkaline batteries will work for four servos, if all of them are moving at once.

Try a 5xAA NiMH battery pack, which can supply much more current than alkaline batteries.

I've been happy with battery packs from all-battery.com.

I assume that AAA was a typo. The article linked to refers to AA servos.

4AA might work for a proof of concept, but I agree with jremingron that they would be marginal. As the batteries discharge, you will be less and less happy with their ability to power the servos.

Use 4 AAA batteries .

No no no, triple-A's are hopeless for this. AA's are probably inadequate too.

4 servos, peak current may be up to 4A, so something with a good amount of grunt is needed.
Find some decent NiMH's with a datasheet and make sure they can handle the current?
A 2S LiPo pack is usually fine with the current, but the voltage is bit too high, alas.

A standard RC 6V receiver pack is the traditional approach, they are likely to have a number
of servos rating too...