Ask HN: Where to buy + (actually) download TV shows?

I find this situation to be interesting enough to post the question about...

For the first time in a while, I actually want to buy a full season of a TV show that I like. Normally, I'd find some other means of getting it that didn't involve money..

The problem is, and I may be blind, but I can't find a single place to purchase and download TV shows. And by download, I mean actually downloading AVI (or some other friendly format) files, for me to do what I want with.

I can't use Amazon because they only support Windows. I can't use iTunes because I use Linux and despise most Apple products. I don't want DVDs because they're pointless, and I want files for the obvious benefits of them (no -- I have no intention on "sharing" them). I can't use an online streaming service because I intend to watch this season on a long flight I'll be taking in a few days.

Am I forced to obtain this season in an unlawful manner, or is there something out there that fits my (basic) needs?