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.
SilverStone 6ポートSATA Gen3 (6Gbps)Non-RAID PCI Express Gen3 x2 拡充カード SS :20221129194502-01324:Beautiful Life 絆 - 通販 - Yahoo!ショッピング