My solar panel charges mine, keeps it topped up for free!
The Juice one is ok if you happen to stumble across it but I would never go hunting for it. The RavPower is a good brand but buy it expecting the solar panel to be a cosmetic only thing, don’t actually expect it to work!
I agree that solar panels need to become more powerful. One of the reasons I mentioned the ravpower was because the juice one is a bad price. (Got mixed up with the thread I was replying to if anyone saw this comment before I edited it)
That’s half the problem. With a separate solar panel you can keep the power bank in the shade. Anyway, by all means if you can get a good brand power bank with solar for a similar price than one without then give it a go but in my years of fiddling with these things I have never found one that does as it claims. But just for sanity, find the dimensions of a 10W fold out one then work out the surface area of the one on the power bank and that should answer your question!