A little while ago I noticed the Metz Mecalight S500, liked what I saw, and wanted to research it a bit more before perhaps buying it. At the time there wasn't much information about it, but I did discover a rather similar product, namely the Iwata GL-01, which as far as I can make out is an identical product.
At the time the Metz was selling for £120, and the Iwata £60 (at the time of writing the Metz has got cheaper, and the Iwata more expensive).
My point here is that Metz have seemingly taken someone else's product, slapped their name on it, and promptly doubled the price.
Cheeky Metz! The benefits of having a big (ish) name that people know and trust.
Anyway, I ended up purchasing the Iwata version, and I've been very impressed.
It throws out enough light to blind most people, and you can adjust the colour temperature between 3000 and 5500 k. It charges via USB (micro usb), and the light output is adjustable between 5% and 100% . It's even got a tripod mount on its underside.
Oh, and its around the size of a small smart phone, so you can easily slip it into your shirt pocket and hardly notice its there.
Highly recommended - you can buy the Iwata via this Amazon link - https://amzn.to/2CZ52q8