I just replaced a battery in my Nevo SL with one from worcell.
The only one i could find online with the same (replacemend) type for a nice price.
Type: 523759 1450mAh (Li-Po) Li-Polymer Cell
Battery price just €11.70
Shipping Cost: €7.20
Total cost: €18.90
It was out of stock when ordering and when shipped it needed some weeks (not the fastest shipping).
After installing it seems to work just fine (battery was already charged).
Just running it for 1 hour. More details later on how it performs.
It does not include the charge protection PCB and 4 wire connector which i used from the old SL battery. [Link: worcell.com]