With the advent of M.2 NVMe SSDs, the market for that type of adapter has dried up, along with what's available in the market place. Back in the day I had a couple of Apricorn adapters, a Solo and a Duo. Sold those years ago.
There's a used Solo on eBay:
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Amazon has the Accelesior S (Same Price as OWC):
OWC Accelsior S is the simple solution to add a high speed SATA 6G drive to PCs or silver Mac Pro towers otherwise restricted to SATA 3G architecture. Combined with a high-performance SSD, Accelsior S brings cutting edge SATA 6G performance to your SATA 3G system. With more than 500MB/s of throug...
They also have this one - I know nothing about it, but there is no magic associated with a device like this, so should work, and Amazon's return policy with allow you to return it if it's a no-go:
Boost system speed and performance by adding a PCIe NVMe U.2 SSD to your PC Simplify system builds with a U.2 to PCIe adapter that mounts your SSD directly to the adapter, with no need for adapter cables. PCI Express 3.0 x4 lane host adapter Connect your 2.5" NVMe SSD (U.2 / SFF-8639 interface) t...
That thread posted above is way out of date. Most of the cards listed are no longer being manufactured.