[cctalk] NTSC TV demodulator

I have a couple of 70s/80s "home" computers (e.g. Radio Shack Color Computer) that are intended to connect to a TV set. They don't have easily available composite video, even internally, only modulated RF output. Currently I have an old CRT TV that I use with them, but for various reasons that isn't practical long-term. Does anyone know of a small TV tuner that tunes old analog TV channels (US NTSC) and outputs composite or VGA or HDMI signals? I've looked around a bit but haven't found anything. It's relatively easy to build one, but I would prefer a pre-built solution. And I'm sure others have run into this same problem. Thanks, Will