I've been shopping for sling swivels lately, particularly nickel-plated or stainless steel ones. I realize you probably don't want that, but the same ones are almost always offered in some type of black or blued finish since that is so much more popular.
I am going to limit what I show to some options other than the Uncle Mikes type you already displayed, but that still use the traditional stud. If you go away from the traditional stud to some other mount, there are even more options.
Here's the Booney Packer:
This one below is the Talon push-button side-release from Outdoor Connection without the safety screw-down
:
Note that the Uncle Mikes knurled screws covers are plastic. You can get knurled screws from other makers like Grovtec, Detroit Leather, and Trirock that have metal knurled covers.
The ones below are also from Outdoor Connection, called the Titan. They come in black or gray and appear to be powder-coated:
These use a spring-loaded detent plunger against the brass-colored stud.
The Allen QD swivels below are somewhat conventional in design, but they are remarkable for making them much stronger than typical. They're rated for "over 500 lbs".
Another option is to keep the traditional stud mounts on the rifle, but use a conversion adapter to another style. I can think of two meaningful ways to do this.
First, is with a simple wire bail, and then using a J-hook to clip into it.
This hook is from Blue Force Gear:
Here is another type of cable hook:
The other way to adapt is to the push-button quick-release:
Above is from ATI; below is from Samson
Those convert to the push-button QR. I can't possibly show all the possible swivels that will work with those, but I'll show one just to be clear what fits the above two adapters. This one is from Magpul: