Amazon.com: KingSpec 512GB M.2 NVMe SSD, 2242 PCIe Gen3x2 Internal Solid State Drive for Laptop/Notebook (2242, 512GB) : Electronics
SKHynix 512GB 256GB PCIe Gen3 x 2 M.2 2242 NVMe SSD HFM512GDHTNG-8310A BA SSD | eBay
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: KingSpec 1TB M.2 NVMe SSD, 2242 PCIe Gen3x2 Internal Solid State Drive for Laptop/Notebook (2242, 1TB) : Electronics