Where would I buy " Adventure Time " cartoon on series on DVD?

You might think this is weird about a 19 year old wanting this cartoon
on DVD.
Sadly I think Flapjack was canceled or something, and Adventure Time
is the next best thing.
I've looked on Amazon and Ebay and found nothing. I have also looked
at Best buys website and still nothing.

Is this something a company will have to order for me ?