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.
Apacer AS2280P2 SSD Price in BD | RYANS
Buy the Transcend 128GB, M.2 2242, PCIe Gen3x2, NVMe, 3D TLC BiCS5, DRAM-less,... ( TS128GMTE460T-I ) online - PBTech.co.nz
What is the difference between PCIe Gen 3 X2 and X4 SSDs? Can these two SSDs be used for laptops that support the PCIe interface? - Quora