I harvested a PCIe Gen3 x2 NVMe 1.3 SSD from my older laptop, the problem is that its length is short. I've held it in place with some tape, it should hold.
ECS06, 6 Ports SATA Gen3(6Gbps) port multiplier, Non-RAID, PCI Express Gen3 x2 card, 1 - Kroger
Amazon.com: PCIe Gen3 x2 USB 3.2/3.1 Card ASM3142- PCI Express to 4-Port Type C HUB Internal Expansion Card Controller Adapter PCI Express Card Desktop PC Support Multiple INs : Electronics
Amazon.com: PCIe Gen3 x2 USB 3.2/3.1 Card ASM3142- PCI Express to 4-Port Type C HUB Internal Expansion Card Controller Adapter PCI Express Card Desktop PC Support Multiple INs : Electronics
Amazon.com: LINKUP - Premium Tool-Less NVMe SSD 10 Gbps Enclosure M.2 to USB-C | Aluminum USB 3.1 Gen 2 to PCIe Gen3 x2 Bridge Chip for Windows & Mac | Compatible with
PCIe Gen3 x2 to Type E Card PCI Express to Internal Type E Front Panel USB3.2 | eBay
Corsair Force Series Mp300 Ssd 120gb 240gb Nvme Pcie Gen3 X2 M.2 Ssd 480gb 960gb Solid State Storage 3,000mb/s M.2 2280 Laptop - Solid State Drives - AliExpress
Amazon.com: PCIe Gen3 x2 USB 3.2/3.1 Card - PCI Express to 5-Port[Type C (2), Type A (3) ] USB 3.2 HUB Internal Expansion Card Contronller Adapter PCI Express Card Desktop PC Support Multiple INs : Electronics
Amazon.com: KingSpec 512GB M.2 NVMe SSD, 2242 PCIe Gen3x2 Internal Solid State Drive for Laptop/Notebook (2242, 512GB) : Electronics
MP32 M.2 PCIe SSD│TEAMGROUP
NGP80_NEW Western Digital PC SN520 SDAPTUW-256G 256GB M.2 2230 Nvme Pcie GEN3 X2 SSD NGP80 M.2 SSD / Solid State Drive - Newegg.com
SKHynix 512GB 256GB PCIe Gen3 x 2 M.2 2242 NVMe SSD HFM512GDHTNG-8310A BA SSD | eBay