Theoretically, this 1TB M.2 2230 SSD should be compatible with the steam deck and might be a great addition to a 64GB model for adventurous modders : r/SteamDeck
SN530 m.2 2230 SSD 1TB NVMe PCIe for Microsoft Surface Pro X Surface Laptop 3 - Walmart.com
Amazon.com: Samsung 1TB SSD M.2 2230 30mm PM991a NVMe PCIe Gen3 x4 MZ9LQ1T0HBLB Solid State Drive for Surface Pro Steam Deck Dell HP Lenovo Laptop Ultrabook Tablet : Electronics
Amazon.com: Western Digital 1TB SSD PC SN530 M.2 2230 PCIe Gen3 x4 NVMe 1024GB SDBPTPZ-1T00 : Electronics
Inland TN436 1TB 3D TLC NAND PCIe Gen 4 x4 NVMe M.2 2230 Internal SSD - Compatible with Microsoft Surface and Steam Deck - Micro Center
Wd Sn530 M.2 2230 Ssd 1tb Nvme Pcie For Microsoft Surface Pro X Surface Laptop 3 - Solid State Drives - AliExpress
SN530 m.2 2230 SSD 1TB NVMe PCIe for Microsoft Surface Pro X Surface Laptop 3 | RTBShopper
Kioxia BG4 1TB M.2 2230 SSD Review | eTeknix
Steam Deck has M.2 2230 SSD slot, but Valve does not recommend upgrading it - VideoCardz.com
1TB M.2 2230 NVMe PCI Express 3.0 x2 SSD (Solid State Drive)-30mm Half Size, Brand : Samsung PM991 MZ-VLQ1T00, KLFGGAR4AA-K0T0 For Microsoft Surface Pro X, Microsoft Surface Pro 7+, Microsoft Surface Laptop
Kioxia launches BG5 Series PCIe 4.0 SSDs in M.2 2230 | Club386
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Toshiba BG4 Single Package M.2 2230 30mm NVMe SSD Review