Here is the information I received from Ebay seller Ladyblue about the Andida 2250 mAh battery:
"I believe the S2-HD Battery will fit. It is the exact same dimensions.
It has 4 pins but the 4th pin is not used (See picture attached)
the first pins is at 8mm from the edge and the 3rd pin is at 13 mm from the edge"
I'm going to give it a try and see if the advertised high-capacity pans out, as I'd also like to find something with a bit more juice than that the stock 1850 mAh, without going to a fat-back 3800.