XG1v4 DVR Cable Box Purchase

Hi,

Where can I buy an XG1v4 Cable Box or similar DVR and non-DVR Cable Box outright, so I don't have to pay this additional monthly fee for cable box use?

I went on Best Buy online and Amazon, but nothing.  All my searches ended up with regular Digital DVR for regular on-air broadcasting NOT for Comcast Xfinity Service.

I found a bunch of used cable boxes on eBay, but I'm sure Comcast blocks them.

Thank you,

Mark