You might be stuck with the one you linked. You could polish it by hand or by Dremel to make it shinier. This might be the best bet. And even if you don't need t, you'll have the adjustable gas block feature if you ever do.
You could get a regular one, polish it, or have it polished, then have it chrome or nickel plated. The cost to have this done might be way to high though, especially if you have the plater do the polishing. That will be a very labor intensive job to make it look good when plated. If it's not perfect, every little flaw will show.
If it were me, and I couldn't find any others, which I can't remember ever seeing, I'd get the adjustable and spend a couple hours with some rags and a tube of Flitz polish while watching some TV or a movie.
And for the people thinking he meant adjustable as in adjusting the sight, not it being an adjustable gas block, especially with a freaking web address posted.... well, you know how ar15.com gets trash talked on parts of the internet and in real life? Like how Vickers got everyone butthurt about the people who were copy repairmen during the day and posted on ar15.com from their mom's basements all night? Yeah, you're the ones who give everyone here a bad rep.