An exceptionally trivial model, but I couldn't find anything similar so I made it: when the Steam Deck is docked (on the official one anyway) this goes on top and covers the screen, leaving the air vents free to do their work. Printed mine in transparent red PET, didn't come out looking perfect but otherwise is fine. Very flimsy, won't protect from anything aside dust. It's bigger than you think, almost 18cm so it won't be printable on every printer.