wow. an SSD for ps5 is less $ for twice the size as steam deck. steam deck replacements are too expensive to make it worth it.Just use an SD card. Valve managed that game performance is the same from an SSD or SD card.
With that said, get a Steamdeck. I got a GPD Win 3 and I use it daily. I'm actually at the point where I'll setup emulators for the Switch on it and use that instead of my acutal Switch. I have a GPD Win 4 on the way whenever they get shipped out. That will probably be my last handheld I'll be buying for the next 10 years.