vhbw Li-Ion Battery 1050mAh (3.7V) for cordless landline phone Siemens Gigaset SL910, SL910A as V30145-K1310K-X447, V30145-K1310K-X447-0-HY. (Electronics)
Fits just like the original part of Siemens, at half the price. How long does the battery work, I can not say, but what can you go wrong with the price.