I actually bought the bike with that LED taillight on it. I have no idea what brand it is, likely some eBay special. I had to rewire things back there as it had a bunch of wire-nuts and wingdings holding it together.
It's been okay, I need to repaint it (and basically the whole bike). As my wife has followed me while riding in the day, I've asked her how well it illuminates. She says she can see everything quite well, from a distance, in bright daylight, etc.
Sorry, I wish I could tell you the brand - but there's nothing on it (IIRC). It's urethane, it's painted, it flexes, it's a "taillight".
I will double-check it to verify there's no branding but I'm pretty sure it was a generic piece likely made at some point.