A23 battery? 12v small, basically 8 button batteries all packaged up nice and neat. From what I've read and looking at the tealights they each run off 3v so with 12v you can run 4 off one battery that cost between $2 - $4 (one of the videos I watched they guy purchased his from Walmart in the camera/video section for $1.88 for two.)
Battery info
Battery holder
Just one thing the A23 is only rated for 40-65 mah, where the SR44 (AG13) is 110-150 mah which the dollar tree candles takes 2 or a CR2032 is 220-225 mah for other cheap tealights. So the tealights wouldn't last very long? There are SR63 (AG0) which only produce 10-18 mah each, I may have to hack an A23 to find out what's inside.
A23 contain 8 - LR932 1.5 v 4.125 mAh

so they won't last an hour if you're lucky.
Well after about 2 hour of research I've come to a conclusion (sorry about the ramble, but I figured I'd keep it up for others)
To keep this cheap and have the ability to hidden the power source. I'll keep my groups of 3 and add one more candle to the group of 5. For 3 candles you need a
9v battery (they aren't as expensive as I thought and I think you can even get them from the
dollar store) , a
9v Battery snap,
wire (what gauge I don't know), solder and a soldering gun. So if you have the soldering stuff already and for 30 candles your looking at $25.60 and that includes shipping.