You can find any one of these at any big comic book stores. They have anything from the original Superfriends,.. to Thundercats, He-man, Full seasons of everything Transformers, Autobots, Gi Joe, Submariner, etc,..
They even have movies that were never realeased publicly like The Fantastic Four, Captain America, Wonder Woman (not the one with Linda Carter), Batman, etc...
The list goes on and on,... I even found full seasons of The Six Million Dollar Man, The Greatest American Hero, Miami Vice, The Incredible Hulk, etc..
I heard there are comic book conventions that tour across the U.S, and you can find some interesting things that are not even related to comic books.

I purchased the first ever live action Legends of the Superfriends that was made in 1977 from a place around my job.
It had all the Superheroes/ Villains except Superman