Did a bit of a dig around and found this company: Minerva Innovation. Not 100% sure if they are the actual manufacturer but their website seems to offer the largest portfolio and most comprehensive documentation.
In fact, you can use these with 2x 4i → 8i cables and connect them to robust x4 + x4 PCIe slot adapters that are powered by a beefy 6-pin PCIe power, which makes for a great solution to run at stable 4.0 speeds with extra GPUs or HBAs.
Please note that clearance issues are possible. For example, on the W680-ACE, in one of the slots I can’t get the connector to fit due to the chipset heatsink. I think Oculink connectors would be at least as difficult, or maybe more, depending on the length of the hard part of the connector and how close to the end of the M.2 PCB the connector is placed.