Found these rings for the Ultegra 6800.
https://absoluteblack.cc/oval-road-c...for-110-4bcd/#
30/46 & 32/48.
Reading the page, they are doing several optimizations. First of all, the Ultegra 4 bolts aren't oriented on a square, but rather on a rectangle. That allows an oval ring to be used that fits onto the bolt holes better.
Second, they're adding an extra spacer, spacing the small rings off of the spider, and I assume the large ring overhangs slightly to compensate.
Third, they use special bolts. 7mm for the 32, and a mix of 5mm and 7mm for the 30.