Altex sells them.
Frankly I would never use it. I check them out out of curiousity one day and I don't see how it can be good. Shielding is vital in coax, hence the quad shielded coax and all that. Obviously there is a ton of shielding missing from the flat cable.
The other problem is it's still normal cable size on both ends. So, hopefully you're just using it to run under a door or something.
Also the ones I looked at did not have connectors on the end that spun. SO>...assuming you can't turn the devices you're connecting to...I'm not sure how you'll connect the cable with twisting it up. Granted, you could be just hooking it to a barrel connector...
I just think those cables are poorly designed and a bad idea. Don't plan to do high end video/tv/etc stuff with those, they will be the weak point for your center.
My '03 Sold.