The DSE 901 manual battery isn't available yet. The post in the Eastmall forum said they'd have it by the end of the month. Keep in mind:
the new manual 901 batteries require new chargers. They'll work with the USB chargers, but not the AC/wall outlet chargers that came with your automatic batteries in the original kit.
The problem seems to be that the button on the manual switch either won't fit or gets pushed down in the old chargers. Now, someone with some mechanical know-how could probably modify an old charger to work with the new batteries, but as of this moment, if you want the new batteries, you'll either need to buy a new charger or only use it with a USB charger.
Eastmall will also be offering a Portable Charging Case (PCC) for the 901 very soon . . . however, the first ones made also won't work with the manual batteries for the same reason (the switch won't fit in the slot). I believe they've said they'll be fixing this on later releases.
Check their supplier forum for more details.