Can’t purchase movie on Apple tv

So I’m trying to buy the movie Clerks. It’s a movie I’d like to own and have saved in my library collection. There isn’t a Buy option at all. My only option is “Try Cinemax free” for a week followed by a subscription. Not something I really wanna do. I’ve run in to this problem with a few different movies. Is there anyway I can actually buy and keep it saved under my Apple ID?