I can vote for a 'normal' capacity Japod battery, here : http://www.dealextreme.com/details.dx/sku.32398. Lasts more or less the same time, reports a tiny bit less mAh than the Nokia original one and is a bargain for $8.84, incl. shipping.

Easy to carry a spare one around, as I normally do when going out or expecting to be long time away from a power socket.