Casper has had a few cartoon series (Thanks for making me feel old, btw

). The earliest one that comes to mind is
Casper the Friendly Ghost and Company, a selection of re-packaged shorts from Paramount Pictures-retitled "Harveytoons", which premiered in 1974. It was syndicated.
Then there was Hanna-Barbera's
Casper and the Angels (NBC, 1979-1980), which had Casper assinged to help a pair of lady cops in the year 2179, with the "help" of his ghost friend, a new character named Hairy Scary.
Then came the Saturday Morning series simply titled
Casper (FOX, 1996-1997), which was based on the 1995 live action movie.
As for where you could obtain episodes, I assume that you mean legally, in any case, I don't know if that should be discussed here.