Anybody know if Constantine (TV series) is available for purchase?

I loved the Constantine TV series, and I’d like very much to have my own copy of it (on DVD or online, like from iTunes). I have all the episodes on my DVR, but I know eventually something will happen to them (my cats are death on DVRs). Anybody know where I can get a (legal) copy of the series? Or, barring that, any recent news about when it might be available?

Thanks in advance.