I assume you are talking about RG59/RG6 coax or RF cables, not coax digital audio cables?
If so there are some cable manufacturers out there who make RG6 cables that are very flexible and work well, however they tend to be much more expensive. This is one thing that I did actually like about Monster Cable, they made some very nice, flexible RG6 cables. I actually have one RG6 cable that is about 50 foot long where the wire is only about an 1/8" in diameter and very flexible. It actually worked great and I used it for years in my old apartment where I had to run the coax from one wall around the edge of the room to the oppisite wall to get to my HD-DVR. It worked fine with both Comcast HD service as well as DirecTV HD service.
I just checked and Monster doesn't make the really thin cable like I have anymore, but the do seem to still make some of the other cables like I had.
These are much more flexible than regular coax cables, so it might be worth trying out.
And before everyone jumps on me about Monster being a ripoff, etc. I know that and I normally wouldn't recommend them. I usually buy all my cables from Monoprice, but in this particular instance where the poster is looking for a more flexible coax I think this may be an option.