mentioned the Spigen band is great. I found one of those and was recently going to order another just to keep on hand but they're gone. What a shame. Also I agree with the comments regarding their appearance on Amazon. They come and go fast with varying names and seem to be similar products. I ordered one made by Seoaura, will compare it to the Spigen band after receipt and then report back with my thoughts.
Also agree that the knockoff Sport bands are nowhere near as good as Apples. I too only buy the genuine product now. For leather, I use FFF and absolutely love them. Great look, great design, exceptional customer service, by far the most comfortable bands I own and hand made.
Update: I received a Space Gray band from Seoaura today and my initial comparison to the Spigen band is it is a little darker, more black than Space Gray. Spigen is a closer match to Apple's SG but not a 100% match either. It is however close enough. Also it feels slightly heavier than the Spigen version but I cannot confirm that at this point. It does however seem to be of good enough quality for the asking price.
The photos in this link are a bit deceptive as the magnet appears to be rounded and with the product I received, it is more similar to Apple's.
Here are some shots of the two side by side so you can see the color variation. Spigen is on the left, Seoaura is on the right. In the last shot, Spigen is on top, Seoaura is on the bottom.