ebay.com/itm/2430MAH-HIGH-CAPACITY-GOLD-BATTERY-SAMSUNG-S5570-GALAXY-/130568244597
Well, someone over at anythingbutipod said that this battery would work, but I find it to good to be true that they could fit twice the mah in the same size battery. That would be awesome if they did, though.
I bought the battery based on BOBdotEXE's recommendation. It arrived fast from the UK to Wisconsin. I haven't done any scientific testing but in my daily use, the original battery was dropping fast from 100 to 20% charge with extremely light use. My thought is that original battery was going bad. So comparing the new one to a failing OEM, the new one wins!
Bottom line - At a minimum it seems to work the same as the OEM. Possibly a little better.