I wish to BUY a TV tuner box. What are my options?

I wish to BUY a TV tuner box to replace the Pace RNG110 which I currently RENT from Comcast.

I was told by a rep in a Comcast store near me that they only 'rent' devices. However, xfinty.com states that Comcast does allow

'Customer Owned Equipment' to which I will need to add a Cable Card which will be provided to me by Comcast.

What devices qualify & Where can I purchase? Any guidance and recommendations are appreciated.

Thank you.