C pillar bar, none that I have heard of. But, Cusco does make some braces for our car that goes immediately behind the rear seats. You would need to either remove the trunk lining, or cut holes in them where its necessary for them to be mounted up without taking the lining out.
However, as many people have said, the FG and FA are really stiff cars as is. I bought my B pillar bar specifically for a camera mount spot. But After I installed it, I didnt notice any difference at all. Other than going up driveways at an angle. But even then. Not much of a difference.
But C pillar bar would most likely show less. Which would ultimately lead to being a waste of money IMO
Here's the link for the cusco parts. they have a lot of braces, but I personally cant see them being of any use. Other than adding weight.
CUSCO New Products for Civic FD2-Type R