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.
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
Team Group MP32 M.2 2280 256GB PCIe 3.0 x2 with NVMe 1.3 Internal Solid State Drive (SSD) | Help Tech Co. Ltd
Amazon.com: KingSpec 1TB M.2 NVMe SSD, 2242 PCIe Gen3x2 Internal Solid State Drive for Laptop/Notebook (2242, 1TB) : Electronics
PCI-e Gen 3 8-Lane to M.2 NVMe SSD x 2 Dual Port Adapter with Heat Sink