Solar charger for Fairphone 3

[Volker]

As this question is imho not device specific please continue even for the FP3 at this topic:

What solar charger to buy for the FP4

As this thread is already a few years old, I’d like to ask what solar charger you’d recommend for the Fairphone 4. The use case is the window sill of the southern side of my flat, so it should not be too large.