When I bought my Series 3 at launch, I really wanted the Nike Platinum/Black sport loop. It didn’t go on sale, separately, for several months after the Nike Watch S3 debuted (which was well after the non-Nike S3’s just like this year).
So my guess, it will be a while before the reflective band will be available on its own.
There aren't any Nike Sport Loops available in any color. That's the one I'm interested in as well, since I like the black sport loop that I have now, but I'm not crazy about the multicolor threads.
I'm guessing that I'll have to wait six months or so.
They have been selling these 3rd party for years now. I saw the Nike band and thought I was seeing things.
Have a scour through eBay and you will find loads - I have owned 2 of the reflective ones in different colours for the past year! I also have 3 more in zappier colours but they aren't reflective.