PCIe 4.0: Everything you need to know, from specs to compatibility to caveats | PCWorld
PCIe x4 to M2 NVMe extension cable supports NVMe SSD interface PCIE 4.0x4 full speed 64G/bps - AliExpress
PCIe Gen4 x4 Slot - M.2 Adapter - Serial Cables
PCIe Gen 4 vs. Gen 3 Slots, Speeds
Amazon.com: ASUS Hyper M.2 X16 PCIe 4.0 X4 Expansion Card Supports 4 NVMe M.2 (2242/2260/2280/22110) up to 256Gbps for AMD 3rd Ryzen sTRX40, AM4 Socket and Intel VROC NVMe Raid : Electronics
M.2 NVMe SSD PCIe 4.0 Adapter with Covered Heat Sink - Micro Connectors, Inc.
Amazon.com: GELRHONR M.2 NVME to PCIe 4.0x4 Adapter Card for 1U Case,Supports M Key 2280,2260,2242,2230 M.2 Solid State Drives(Do not Support NGFF) : Electronics