Hi,
Based on the photo of the VARTA battery I found a VARTA candidate for it.
What I assumed as the type was 'PLF503759.06.8087/33...'
Based on 503759 and looking for Lithium-Polymer batteries with about 1400 mAh I identified a strong candidate for it.
Have a look at the Varta specifications for
LPP 503759 8HH