In general: Buck Rogers, Flash Gordon, John Carter Captain Video.
TV Shows-Doctor Who, Red Dwarf, Blake's Seven, The Wild Wild West, Star Trek, The Twilight Zone, The Outer limits, Space 1999, Lost in Space, Bablyon 5, Sliders, The Adventures of Brisco County Jr, Farscape, Stargate, Warehouse 13, Andromeda, Firefly, The Expanse, Dark Matter, and Lexx.
The Bulk of 70's/80's 'Space' Cartoons:
Battle of the Planets/G-Force, Bravestar, The Adventures of the Galaxy Rangers, He-Man, The Real Ghostbusters, Silverhawks, Jacye and the Wheeled Warriors, Thundar the Barbarian, Thundercats, Visionarys, Voltron, , Transformers, and The Jetsons.
Now some of the above, like Farscape, Firefly, Lexx and Bravestar are just near pure Spelljammer. And a Firefly Spelljammer game is off to a good start....
Most of them contain magic fantasy in space...except the Expanse. You can find a lot of them on places like Tubi or You Tube. If you see one you don't know, try and find and watch it. Sure the show might be "bad", but just the pure visuals can give and inspire many ideas.
Movies: Well, safe to say nearly all 70-80 sci fi fantasy movies. Flash Gordon(1980) really stands out here as 'pure spelljammer'. And Ice Pirates(just ignore the tech parts).
Books: any of the above. But books are a bit 'dry' for Spelljammer. Though the Xanth books have the near perfect feel.