I found some 9/16 inch CF tubes, but they are the I/D measurement, not O/D.

TUR-09 Carbon Tubes / Roll Wrapped .5625"(9/16")ID x .033"WT x 29.5" $24.00

They do have this one though:
TUR-08 Carbon Tubes / Roll Wrapped .555 ID x .033" WT x 28.5" $25.00 So, what would the O/D be if the ID was .555" plus .033 wall thickness?

Found them from ACP Composites.
[link=http://www.acp-composites.com/acp-tube.htm]ACP Composites[/link]