I can't seem to find one online or even through my distributors. Such a cable might exist somewhere, but it doesn't look like anything has been released to the public yet. The Club3D adapter and an HDMI 2.0 cable is probably your best bet, though it only supports 4/4/4 at 8-bits (if that matters to you). If you have a display that supports true 2160p60 w/ 4/4/4, then that's an expensive display and what does it matter how much the cables cost?
I will buy that adapter if I can't find a cable. 8-bit is enough for me, as the TV won't support more than that anyway. I'm aiming for a 4K TV, and those are not expensive. There are three other reasons. 1 - As I will connect it to a laptop, I'd prefer not having the added bulk of that stiff Club3D adapter next to it. If it was for a desktop then I wouldn't care. 2 - By only using one cable I avoid the possible issue of cables not working as expected together. 3 - I don't even have the TV yet so I'm in no hurry buying cables. If it was down to cost alone I wouldn't care about that either.