Two days ago, I posted about one Flare user modifying his Cherry Mobile Flare to use a 2,100mAh Samsung Galaxy S III battery
However, you need some skill or knowledge in electricity or electronics to modify it.
note: Flare's original battery is only 1,500mAh
Just this morning, when I visited the Flare Facebook Group, one Flare user posted another compatible battery with Flare. He said that there is no need to modify the battery. It only means that you don't need an expert hand to use it on Flare, just insert it and you're good to go.
He used a 2,200mAh battery for LG P970 Optimus Black.
Here's the video by Christopher Malonhao: