cablecard devices

We lease a X1 set top box and remote from Xfinity which costs us $10, - a month. Purchasing a customer owned cablecard device seems to be an option. Xfinity claims they support them and offers a cablecard kit. They also list five (5!) device manufacturers that they support, but when you search Amazon (!), or Walmart, Best Buy, no current models are available or the specifications are awful, e.g. 720dpi HDMI. Otherwise, you may be lucky to find them used on eBay. It's like they support them, but not really. I would like Xfinity to provide a current list of manufacturers and models of devices they support and that are easily available through common retail resources. Thank you.