Amazon.com: ADT-LINK M.2 Key M NVMe External Graphics Card Stand Bracket with PCIe3.0 X4 to Thunderbolt 3 Riser Cable PCI-Express External Adapter Cable EGPU Adapter 25cm 50cm 32Gbs for ITX STX NUC (
If the Steam Deck actually has an open x4 PCIe 3.0 slot you could have an eGPU solution while docked. That many 3.0 lanes is plenty enough bandwidth for something like an
Best eGPU Enclosures – June 2023 External GPU Buyer Guide | eGPU.io