Been using this for last 6 weeks, it's 2000 mah, no errors, working great http://www.amazon.co.uk/gp/product/B000VO6W5M/ref=oh_aui_detailpage_o04_s00?ie=UTF8&psc=1
Just brought a pre owned 3ds pink from game uk - http://www.game.co.uk/en/hardware/nintendo-3ds/?inStockOnly=true&sortTypeStr=DESC&sortColumn=popular&merchname=topnav-_-3DS-_-New3DSConsoles
firmware 4.4.
Other places I would have tried if this didn't work out...